What is the general solution for sin(x)-cos(x)=sqrt(2) ?

The general solution for sin(x)-cos(x)=sqrt(2) is x=2pin+(3pi)/4

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sin(x)-cos(x)=sqrt(2)

Solution

sin (x) - cos (x) = 2

Solution

x = 2 πn + \frac{3 π}{4}

Degrees

x = 13 5^{\circ} + 36 0^{\circ} n

Solution steps

sin (x) - cos (x) = 2

Rewrite using trig identities

sin (x) - cos (x)

sin (x) - cos (x) = 2 sin (x - \frac{π}{4})

sin (x) - cos (x)

Rewrite as

= 2 (\frac{1}{2} sin (x) - \frac{1}{2} cos (x))

Use the following trivial identity:

cos (\frac{π}{4}) = \frac{1}{2}

Use the following trivial identity:

sin (\frac{π}{4}) = \frac{1}{2}

= 2 (cos (\frac{π}{4}) sin (x) - sin (\frac{π}{4}) cos (x))

Use the Angle Sum identity:

sin (s - t) = sin (s) cos (t) - cos (s) sin (t)

= 2 sin (x - \frac{π}{4})

= 2 sin (x - \frac{π}{4})

2 sin (x - \frac{π}{4}) = 2

Divide both sides by

2

2 sin (x - \frac{π}{4}) = 2

Divide both sides by

2

\frac{2 sin ( x - \frac{π}{4} )}{2} = \frac{2}{2}

Simplify

sin (x - \frac{π}{4}) = 1

sin (x - \frac{π}{4}) = 1

General solutions for

sin (x - \frac{π}{4}) = 1

sin (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

x - \frac{π}{4} = \frac{π}{2} + 2 πn

x - \frac{π}{4} = \frac{π}{2} + 2 πn

Solve

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

x - \frac{π}{4} = \frac{π}{2} + 2 πn

Move

\frac{π}{4}

to the right side

x - \frac{π}{4} = \frac{π}{2} + 2 πn

Add

\frac{π}{4}

to both sides

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

Simplify

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

Simplify

x - \frac{π}{4} + \frac{π}{4} : x

x - \frac{π}{4} + \frac{π}{4}

Add similar elements:

- \frac{π}{4} + \frac{π}{4} = 0

= x

Simplify

\frac{π}{2} + 2 πn + \frac{π}{4} : 2 πn + \frac{3 π}{4}

\frac{π}{2} + 2 πn + \frac{π}{4}

Group like terms

= 2 πn + \frac{π}{2} + \frac{π}{4}

Least Common Multiplier of

2, 4 : 4

2, 4

Least Common Multiplier (LCM)

Prime factorization of

2 : 2

2

2

is a prime number, therefore no factorization is possible

= 2

Prime factorization of

4 : 2 \cdot 2

4

4

divides by

24 = 2 \cdot 2

= 2 \cdot 2

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

2

4

= 2 \cdot 2

Multiply the numbers:

2 \cdot 2 = 4

= 4

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

4

For

\frac{π}{2} :

multiply the denominator and numerator by

2

\frac{π}{2} = \frac{π 2}{2 \cdot 2} = \frac{π 2}{4}

= \frac{π 2}{4} + \frac{π}{4}

Since the denominators are equal, combine the fractions:

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

= \frac{π 2 + π}{4}

Add similar elements:

2 π + π = 3 π

= 2 πn + \frac{3 π}{4}

x = 2 πn + \frac{3 π}{4}

x = 2 πn + \frac{3 π}{4}

x = 2 πn + \frac{3 π}{4}

x = 2 πn + \frac{3 π}{4}

Popular Examples

sin(x)=(sqrt(3))/2 ,0<= x<= 2pi

sin (x) = \frac{3}{2}, 0 \leq x \leq 2 π

2sin(θ)=0

2 sin (θ) = 0

-2cos(x)=0

- 2 cos (x) = 0

3cos(θ)+cos(2θ)=-2

3 cos (θ) + cos (2 θ) = - 2

15sin(x)+7=sin(x)

15 sin (x) + 7 = sin (x)

Frequently Asked Questions (FAQ)

What is the general solution for sin(x)-cos(x)=sqrt(2) ?
The general solution for sin(x)-cos(x)=sqrt(2) is x=2pin+(3pi)/4