What is the general solution for sin(x)=cos(3x) ?

The general solution for sin(x)=cos(3x) is x=(pi+4pin)/8 ,x=-(pi+4pin)/4

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

Popular >

sin(x)=cos(3x)

Solution

sin (x) = cos (3 x)

Solution

x = \frac{π + 4 πn}{8}, x = - \frac{π + 4 πn}{4}

Degrees

x = 22. 5^{\circ} + 9 0^{\circ} n, x = - 4 5^{\circ} - 18 0^{\circ} n

Solution steps

sin (x) = cos (3 x)

Rewrite using trig identities

sin (x) = cos (3 x)

Use the following identity:

cos (x) = sin (\frac{π}{2} - x)

sin (x) = sin (\frac{π}{2} - 3 x)

sin (x) = sin (\frac{π}{2} - 3 x)

Apply trig inverse properties

sin (x) = sin (\frac{π}{2} - 3 x)

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

x = \frac{π}{2} - 3 x + 2 πn, x = π - (\frac{π}{2} - 3 x) + 2 πn

x = \frac{π}{2} - 3 x + 2 πn, x = π - (\frac{π}{2} - 3 x) + 2 πn

x = \frac{π}{2} - 3 x + 2 πn : x = \frac{π + 4 πn}{8}

x = \frac{π}{2} - 3 x + 2 πn

Move

3 x

to the left side

x = \frac{π}{2} - 3 x + 2 πn

Add

3 x

to both sides

x + 3 x = \frac{π}{2} - 3 x + 2 πn + 3 x

Simplify

4 x = \frac{π}{2} + 2 πn

4 x = \frac{π}{2} + 2 πn

Divide both sides by

4

4 x = \frac{π}{2} + 2 πn

Divide both sides by

4

\frac{4 x}{4} = \frac{\frac{π}{2}}{4} + \frac{2 πn}{4}

Simplify

\frac{4 x}{4} = \frac{\frac{π}{2}}{4} + \frac{2 πn}{4}

Simplify

\frac{4 x}{4} : x

\frac{4 x}{4}

Divide the numbers:

\frac{4}{4} = 1

= x

Simplify

\frac{\frac{π}{2}}{4} + \frac{2 πn}{4} : \frac{π + 4 πn}{8}

\frac{\frac{π}{2}}{4} + \frac{2 πn}{4}

Apply rule

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

= \frac{\frac{π}{2} + 2 πn}{4}

Join

\frac{π}{2} + 2 πn : \frac{π + 4 πn}{2}

\frac{π}{2} + 2 πn

Convert element to fraction:

2 πn = \frac{2 πn 2}{2}

= \frac{π}{2} + \frac{2 πn \cdot 2}{2}

Since the denominators are equal, combine the fractions:

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

= \frac{π + 2 πn \cdot 2}{2}

Multiply the numbers:

2 \cdot 2 = 4

= \frac{π + 4 πn}{2}

= \frac{\frac{π + 4 πn}{2}}{4}

Apply the fraction rule:

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

= \frac{π + 4 πn}{2 \cdot 4}

Multiply the numbers:

2 \cdot 4 = 8

= \frac{π + 4 πn}{8}

x = \frac{π + 4 πn}{8}

x = \frac{π + 4 πn}{8}

x = \frac{π + 4 πn}{8}

x = π - (\frac{π}{2} - 3 x) + 2 πn : x = - \frac{π + 4 πn}{4}

x = π - (\frac{π}{2} - 3 x) + 2 πn

Expand

π - (\frac{π}{2} - 3 x) + 2 πn : π - \frac{π}{2} + 3 x + 2 πn

π - (\frac{π}{2} - 3 x) + 2 πn

- (\frac{π}{2} - 3 x) : - \frac{π}{2} + 3 x

- (\frac{π}{2} - 3 x)

Distribute parentheses

= - (\frac{π}{2}) - (- 3 x)

Apply minus-plus rules

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

= - \frac{π}{2} + 3 x

= π - \frac{π}{2} + 3 x + 2 πn

x = π - \frac{π}{2} + 3 x + 2 πn

Move

3 x

to the left side

x = π - \frac{π}{2} + 3 x + 2 πn

Subtract

3 x

from both sides

x - 3 x = π - \frac{π}{2} + 3 x + 2 πn - 3 x

Simplify

- 2 x = π - \frac{π}{2} + 2 πn

- 2 x = π - \frac{π}{2} + 2 πn

Divide both sides by

- 2

- 2 x = π - \frac{π}{2} + 2 πn

Divide both sides by

- 2

\frac{- 2 x}{- 2} = \frac{π}{- 2} - \frac{\frac{π}{2}}{- 2} + \frac{2 πn}{- 2}

Simplify

\frac{- 2 x}{- 2} = \frac{π}{- 2} - \frac{\frac{π}{2}}{- 2} + \frac{2 πn}{- 2}

Simplify

\frac{- 2 x}{- 2} : x

\frac{- 2 x}{- 2}

Apply the fraction rule:

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

= \frac{2 x}{2}

Divide the numbers:

\frac{2}{2} = 1

= x

Simplify

\frac{π}{- 2} - \frac{\frac{π}{2}}{- 2} + \frac{2 πn}{- 2} : - \frac{π + 4 πn}{4}

\frac{π}{- 2} - \frac{\frac{π}{2}}{- 2} + \frac{2 πn}{- 2}

Apply rule

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

= \frac{π - \frac{π}{2} + 2 πn}{- 2}

Apply the fraction rule:

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

= - \frac{π - \frac{π}{2} + 2 πn}{2}

Join

π - \frac{π}{2} + 2 πn : \frac{π + 4 πn}{2}

π - \frac{π}{2} + 2 πn

Convert element to fraction:

π = \frac{π 2}{2}, 2 πn = \frac{2 πn 2}{2}

= \frac{π 2}{2} - \frac{π}{2} + \frac{2 πn \cdot 2}{2}

Since the denominators are equal, combine the fractions:

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

= \frac{π 2 - π + 2 πn \cdot 2}{2}

π 2 - π + 2 πn \cdot 2 = π + 4 πn

π 2 - π + 2 πn \cdot 2

Add similar elements:

2 π - π = π

= π + 2 \cdot 2 πn

Multiply the numbers:

2 \cdot 2 = 4

= π + 4 πn

= \frac{π + 4 πn}{2}

= - \frac{\frac{π + 4 πn}{2}}{2}

Simplify

\frac{\frac{π + 4 πn}{2}}{2} : \frac{π + 4 πn}{4}

\frac{\frac{π + 4 πn}{2}}{2}

Apply the fraction rule:

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

= \frac{π + 4 πn}{2 \cdot 2}

Multiply the numbers:

2 \cdot 2 = 4

= \frac{π + 4 πn}{4}

= - \frac{π + 4 πn}{4}

x = - \frac{π + 4 πn}{4}

x = - \frac{π + 4 πn}{4}

x = - \frac{π + 4 πn}{4}

x = \frac{π + 4 πn}{8}, x = - \frac{π + 4 πn}{4}

x = \frac{π + 4 πn}{8}, x = - \frac{π + 4 πn}{4}

Popular Examples

solvefor x,y=5sin(x/4)solve for

x, y = 5 sin (\frac{x}{4})

3sin(pi/3 x)=2

3 sin (\frac{π}{3} x) = 2

cos^2(x)= 1/3

cos^{2} (x) = \frac{1}{3}

4cos(θ)=1+2cos(θ)

4 cos (θ) = 1 + 2 cos (θ)

tan(θ)= 3/(sqrt(3))

tan (θ) = \frac{3}{3}

Frequently Asked Questions (FAQ)

What is the general solution for sin(x)=cos(3x) ?
The general solution for sin(x)=cos(3x) is x=(pi+4pin)/8 ,x=-(pi+4pin)/4