What is the general solution for cos(2x-15)=-sin(60-3x) ?

The general solution for cos(2x-15)=-sin(60-3x) is x=(4320n+1980)/(60),x=180+360n-45

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cos(2x-15)=-sin(60-3x)

Solution

cos (2 x - 1 5^{\circ}) = - sin (6 0^{\circ} - 3 x)

Solution

x = \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{60}, x = 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

Radians

x = \frac{\frac{11 π}{5}}{12} + \frac{\frac{24 π}{5}}{12} n, x = π - \frac{π}{4} + 2 πn

Solution steps

cos (2 x - 1 5^{\circ}) = - sin (6 0^{\circ} - 3 x)

Rewrite using trig identities

cos (2 x - 1 5^{\circ}) = - sin (6 0^{\circ} - 3 x)

Use the following identity:

- sin (x) = sin (- x)

cos (2 x - 1 5^{\circ}) = sin (- (6 0^{\circ} - 3 x))

Use the following identity:

cos (x) = sin (9 0^{\circ} - x)

cos (2 x - 1 5^{\circ}) = sin (9 0^{\circ} - (2 x - 1 5^{\circ}))

cos (2 x - 1 5^{\circ}) = sin (9 0^{\circ} - (2 x - 1 5^{\circ}))

Apply trig inverse properties

cos (2 x - 1 5^{\circ}) = sin (9 0^{\circ} - (2 x - 1 5^{\circ}))

sin (x) = sin (y) \Rightarrow x = y + 2 π n, x = π - y + 2 π n

- (6 0^{\circ} - 3 x) = 9 0^{\circ} - (2 x - 1 5^{\circ}) + 36 0^{\circ} n, - (6 0^{\circ} - 3 x) = 18 0^{\circ} - (9 0^{\circ} - (2 x - 1 5^{\circ})) + 36 0^{\circ} n

- (6 0^{\circ} - 3 x) = 9 0^{\circ} - (2 x - 1 5^{\circ}) + 36 0^{\circ} n, - (6 0^{\circ} - 3 x) = 18 0^{\circ} - (9 0^{\circ} - (2 x - 1 5^{\circ})) + 36 0^{\circ} n

- (6 0^{\circ} - 3 x) = 9 0^{\circ} - (2 x - 1 5^{\circ}) + 36 0^{\circ} n : x = \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{60}

- (6 0^{\circ} - 3 x) = 9 0^{\circ} - (2 x - 1 5^{\circ}) + 36 0^{\circ} n

Expand

- (6 0^{\circ} - 3 x) : - 6 0^{\circ} + 3 x

- (6 0^{\circ} - 3 x)

Distribute parentheses

= - (6 0^{\circ}) - (- 3 x)

Apply minus-plus rules

- (- a) = a, - (a) = - a

= - 6 0^{\circ} + 3 x

Expand

9 0^{\circ} - (2 x - 1 5^{\circ}) + 36 0^{\circ} n : - 2 x + 36 0^{\circ} n + 10 5^{\circ}

9 0^{\circ} - (2 x - 1 5^{\circ}) + 36 0^{\circ} n

- (2 x - 1 5^{\circ}) : - 2 x + 1 5^{\circ}

- (2 x - 1 5^{\circ})

Distribute parentheses

= - (2 x) - (- 1 5^{\circ})

Apply minus-plus rules

- (- a) = a, - (a) = - a

= - 2 x + 1 5^{\circ}

= 9 0^{\circ} - 2 x + 1 5^{\circ} + 36 0^{\circ} n

Simplify

9 0^{\circ} - 2 x + 1 5^{\circ} + 36 0^{\circ} n : - 2 x + 36 0^{\circ} n + 10 5^{\circ}

9 0^{\circ} - 2 x + 1 5^{\circ} + 36 0^{\circ} n

Group like terms

= - 2 x + 36 0^{\circ} n + 9 0^{\circ} + 1 5^{\circ}

Least Common Multiplier of

2, 12 : 12

2, 12

Least Common Multiplier (LCM)

Prime factorization of

2 : 2

2

2

is a prime number, therefore no factorization is possible

= 2

Prime factorization of

12 : 2 \cdot 2 \cdot 3

12

12

divides by

212 = 6 \cdot 2

= 2 \cdot 6

6

divides by

26 = 3 \cdot 2

= 2 \cdot 2 \cdot 3

2, 3

are all prime numbers, therefore no further factorization is possible

= 2 \cdot 2 \cdot 3

Multiply each factor the greatest number of times it occurs in either

2

12

= 2 \cdot 2 \cdot 3

Multiply the numbers:

2 \cdot 2 \cdot 3 = 12

= 12

Adjust Fractions based on the LCM

Multiply each numerator by the same amount needed to multiply its

corresponding denominator to turn it into the LCM

12

For

9 0^{\circ} :

multiply the denominator and numerator by

6

9 0^{\circ} = \frac{18 0 ^{\circ} 6}{2 \cdot 6} = 9 0^{\circ}

= 9 0^{\circ} + 1 5^{\circ}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{18 0 ^{\circ} 6 + 18 0 ^{\circ}}{12}

Add similar elements:

108 0^{\circ} + 18 0^{\circ} = 126 0^{\circ}

= - 2 x + 36 0^{\circ} n + 10 5^{\circ}

= - 2 x + 36 0^{\circ} n + 10 5^{\circ}

- 6 0^{\circ} + 3 x = - 2 x + 36 0^{\circ} n + 10 5^{\circ}

Move

6 0^{\circ}

to the right side

- 6 0^{\circ} + 3 x = - 2 x + 36 0^{\circ} n + 10 5^{\circ}

Add

6 0^{\circ}

to both sides

- 6 0^{\circ} + 3 x + 6 0^{\circ} = - 2 x + 36 0^{\circ} n + 10 5^{\circ} + 6 0^{\circ}

Simplify

- 6 0^{\circ} + 3 x + 6 0^{\circ} = - 2 x + 36 0^{\circ} n + 10 5^{\circ} + 6 0^{\circ}

Simplify

- 6 0^{\circ} + 3 x + 6 0^{\circ} : 3 x

- 6 0^{\circ} + 3 x + 6 0^{\circ}

Add similar elements:

- 6 0^{\circ} + 6 0^{\circ} = 0

= 3 x

Simplify

- 2 x + 36 0^{\circ} n + 10 5^{\circ} + 6 0^{\circ} : - 2 x + 36 0^{\circ} n + 16 5^{\circ}

- 2 x + 36 0^{\circ} n + 10 5^{\circ} + 6 0^{\circ}

Least Common Multiplier of

12, 3 : 12

12, 3

Least Common Multiplier (LCM)

Prime factorization of

12 : 2 \cdot 2 \cdot 3

12

12

divides by

212 = 6 \cdot 2

= 2 \cdot 6

6

divides by

26 = 3 \cdot 2

= 2 \cdot 2 \cdot 3

2, 3

are all prime numbers, therefore no further factorization is possible

= 2 \cdot 2 \cdot 3

Prime factorization of

3 : 3

3

3

is a prime number, therefore no factorization is possible

= 3

Multiply each factor the greatest number of times it occurs in either

12

3

= 2 \cdot 2 \cdot 3

Multiply the numbers:

2 \cdot 2 \cdot 3 = 12

= 12

Adjust Fractions based on the LCM

Multiply each numerator by the same amount needed to multiply its

corresponding denominator to turn it into the LCM

12

For

6 0^{\circ} :

multiply the denominator and numerator by

4

6 0^{\circ} = \frac{18 0 ^{\circ} 4}{3 \cdot 4} = 6 0^{\circ}

= 10 5^{\circ} + 6 0^{\circ}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{126 0 ^{\circ} + 18 0 ^{\circ} 4}{12}

Add similar elements:

126 0^{\circ} + 72 0^{\circ} = 198 0^{\circ}

= - 2 x + 36 0^{\circ} n + 16 5^{\circ}

3 x = - 2 x + 36 0^{\circ} n + 16 5^{\circ}

3 x = - 2 x + 36 0^{\circ} n + 16 5^{\circ}

3 x = - 2 x + 36 0^{\circ} n + 16 5^{\circ}

Move

2 x

to the left side

3 x = - 2 x + 36 0^{\circ} n + 16 5^{\circ}

Add

2 x

to both sides

3 x + 2 x = - 2 x + 36 0^{\circ} n + 16 5^{\circ} + 2 x

Simplify

5 x = 36 0^{\circ} n + 16 5^{\circ}

5 x = 36 0^{\circ} n + 16 5^{\circ}

Divide both sides by

5

5 x = 36 0^{\circ} n + 16 5^{\circ}

Divide both sides by

5

\frac{5 x}{5} = \frac{36 0 ^{\circ} n}{5} + \frac{16 5 ^{\circ}}{5}

Simplify

\frac{5 x}{5} = \frac{36 0 ^{\circ} n}{5} + \frac{16 5 ^{\circ}}{5}

Simplify

\frac{5 x}{5} : x

\frac{5 x}{5}

Divide the numbers:

\frac{5}{5} = 1

= x

Simplify

\frac{36 0 ^{\circ} n}{5} + \frac{16 5 ^{\circ}}{5} : \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{60}

\frac{36 0 ^{\circ} n}{5} + \frac{16 5 ^{\circ}}{5}

Apply rule

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{36 0 ^{\circ} n + 16 5 ^{\circ}}{5}

Join

36 0^{\circ} n + 16 5^{\circ} : \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{12}

36 0^{\circ} n + 16 5^{\circ}

Convert element to fraction:

36 0^{\circ} n = \frac{36 0 ^{\circ} n 12}{12}

= \frac{36 0 ^{\circ} n \cdot 12}{12} + 16 5^{\circ}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{36 0 ^{\circ} n \cdot 12 + 198 0 ^{\circ}}{12}

Multiply the numbers:

2 \cdot 12 = 24

= \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{12}

= \frac{\frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{12}}{5}

Apply the fraction rule:

\frac{\frac{b}{c}}{a} = \frac{b}{c \cdot a}

= \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{12 \cdot 5}

Multiply the numbers:

12 \cdot 5 = 60

= \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{60}

x = \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{60}

x = \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{60}

x = \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{60}

- (6 0^{\circ} - 3 x) = 18 0^{\circ} - (9 0^{\circ} - (2 x - 1 5^{\circ})) + 36 0^{\circ} n : x = 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

- (6 0^{\circ} - 3 x) = 18 0^{\circ} - (9 0^{\circ} - (2 x - 1 5^{\circ})) + 36 0^{\circ} n

Expand

- (6 0^{\circ} - 3 x) : - 6 0^{\circ} + 3 x

- (6 0^{\circ} - 3 x)

Distribute parentheses

= - (6 0^{\circ}) - (- 3 x)

Apply minus-plus rules

- (- a) = a, - (a) = - a

= - 6 0^{\circ} + 3 x

Expand

18 0^{\circ} - (9 0^{\circ} - (2 x - 1 5^{\circ})) + 36 0^{\circ} n : 18 0^{\circ} + 2 x - 10 5^{\circ} + 36 0^{\circ} n

18 0^{\circ} - (9 0^{\circ} - (2 x - 1 5^{\circ})) + 36 0^{\circ} n

Expand

9 0^{\circ} - (2 x - 1 5^{\circ}) : - 2 x + 10 5^{\circ}

9 0^{\circ} - (2 x - 1 5^{\circ})

- (2 x - 1 5^{\circ}) : - 2 x + 1 5^{\circ}

- (2 x - 1 5^{\circ})

Distribute parentheses

= - (2 x) - (- 1 5^{\circ})

Apply minus-plus rules

- (- a) = a, - (a) = - a

= - 2 x + 1 5^{\circ}

= 9 0^{\circ} - 2 x + 1 5^{\circ}

Simplify

9 0^{\circ} - 2 x + 1 5^{\circ} : - 2 x + 10 5^{\circ}

9 0^{\circ} - 2 x + 1 5^{\circ}

Group like terms

= - 2 x + 9 0^{\circ} + 1 5^{\circ}

Least Common Multiplier of

2, 12 : 12

2, 12

Least Common Multiplier (LCM)

Prime factorization of

2 : 2

2

2

is a prime number, therefore no factorization is possible

= 2

Prime factorization of

12 : 2 \cdot 2 \cdot 3

12

12

divides by

212 = 6 \cdot 2

= 2 \cdot 6

6

divides by

26 = 3 \cdot 2

= 2 \cdot 2 \cdot 3

2, 3

are all prime numbers, therefore no further factorization is possible

= 2 \cdot 2 \cdot 3

Multiply each factor the greatest number of times it occurs in either

2

12

= 2 \cdot 2 \cdot 3

Multiply the numbers:

2 \cdot 2 \cdot 3 = 12

= 12

Adjust Fractions based on the LCM

Multiply each numerator by the same amount needed to multiply its

corresponding denominator to turn it into the LCM

12

For

9 0^{\circ} :

multiply the denominator and numerator by

6

9 0^{\circ} = \frac{18 0 ^{\circ} 6}{2 \cdot 6} = 9 0^{\circ}

= 9 0^{\circ} + 1 5^{\circ}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{18 0 ^{\circ} 6 + 18 0 ^{\circ}}{12}

Add similar elements:

108 0^{\circ} + 18 0^{\circ} = 126 0^{\circ}

= - 2 x + 10 5^{\circ}

= - 2 x + 10 5^{\circ}

= 18 0^{\circ} - (- 2 x + 10 5^{\circ}) + 36 0^{\circ} n

- (- 2 x + 10 5^{\circ}) : 2 x - 10 5^{\circ}

- (- 2 x + 10 5^{\circ})

Distribute parentheses

= - (- 2 x) - (10 5^{\circ})

Apply minus-plus rules

- (- a) = a, - (a) = - a

= 2 x - 10 5^{\circ}

= 18 0^{\circ} + 2 x - 10 5^{\circ} + 36 0^{\circ} n

- 6 0^{\circ} + 3 x = 18 0^{\circ} + 2 x - 10 5^{\circ} + 36 0^{\circ} n

Move

6 0^{\circ}

to the right side

- 6 0^{\circ} + 3 x = 18 0^{\circ} + 2 x - 10 5^{\circ} + 36 0^{\circ} n

Add

6 0^{\circ}

to both sides

- 6 0^{\circ} + 3 x + 6 0^{\circ} = 18 0^{\circ} + 2 x - 10 5^{\circ} + 36 0^{\circ} n + 6 0^{\circ}

Simplify

- 6 0^{\circ} + 3 x + 6 0^{\circ} = 18 0^{\circ} + 2 x - 10 5^{\circ} + 36 0^{\circ} n + 6 0^{\circ}

Simplify

- 6 0^{\circ} + 3 x + 6 0^{\circ} : 3 x

- 6 0^{\circ} + 3 x + 6 0^{\circ}

Add similar elements:

- 6 0^{\circ} + 6 0^{\circ} = 0

= 3 x

Simplify

18 0^{\circ} + 2 x - 10 5^{\circ} + 36 0^{\circ} n + 6 0^{\circ} : 2 x + 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

18 0^{\circ} + 2 x - 10 5^{\circ} + 36 0^{\circ} n + 6 0^{\circ}

Group like terms

= 2 x + 18 0^{\circ} + 36 0^{\circ} n + 6 0^{\circ} - 10 5^{\circ}

Least Common Multiplier of

3, 12 : 12

3, 12

Least Common Multiplier (LCM)

Prime factorization of

3 : 3

3

3

is a prime number, therefore no factorization is possible

= 3

Prime factorization of

12 : 2 \cdot 2 \cdot 3

12

12

divides by

212 = 6 \cdot 2

= 2 \cdot 6

6

divides by

26 = 3 \cdot 2

= 2 \cdot 2 \cdot 3

2, 3

are all prime numbers, therefore no further factorization is possible

= 2 \cdot 2 \cdot 3

Multiply each factor the greatest number of times it occurs in either

3

12

= 3 \cdot 2 \cdot 2

Multiply the numbers:

3 \cdot 2 \cdot 2 = 12

= 12

Adjust Fractions based on the LCM

Multiply each numerator by the same amount needed to multiply its

corresponding denominator to turn it into the LCM

12

For

6 0^{\circ} :

multiply the denominator and numerator by

4

6 0^{\circ} = \frac{18 0 ^{\circ} 4}{3 \cdot 4} = 6 0^{\circ}

= 6 0^{\circ} - 10 5^{\circ}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{18 0 ^{\circ} 4 - 126 0 ^{\circ}}{12}

Add similar elements:

72 0^{\circ} - 126 0^{\circ} = - 54 0^{\circ}

= \frac{- 54 0 ^{\circ}}{12}

Apply the fraction rule:

\frac{- a}{b} = - \frac{a}{b}

= - 4 5^{\circ}

Cancel the common factor:

3

= 2 x + 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

3 x = 2 x + 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

3 x = 2 x + 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

3 x = 2 x + 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

Move

2 x

to the left side

3 x = 2 x + 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

Subtract

2 x

from both sides

3 x - 2 x = 2 x + 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ} - 2 x

Simplify

x = 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

x = 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

x = \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{60}, x = 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

x = \frac{432 0 ^{\circ} n + 198 0 ^{\circ}}{60}, x = 18 0^{\circ} + 36 0^{\circ} n - 4 5^{\circ}

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Frequently Asked Questions (FAQ)

What is the general solution for cos(2x-15)=-sin(60-3x) ?
The general solution for cos(2x-15)=-sin(60-3x) is x=(4320n+1980)/(60),x=180+360n-45