What is the general solution for cos(x-pi/4)+sin(x+pi/4)=0 ?

The general solution for cos(x-pi/4)+sin(x+pi/4)=0 is x=(3pi)/4+pin

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cos(x-pi/4)+sin(x+pi/4)=0

Solution

cos (x - \frac{π}{4}) + sin (x + \frac{π}{4}) = 0

Solution

x = \frac{3 π}{4} + πn

Degrees

x = 13 5^{\circ} + 18 0^{\circ} n

Solution steps

cos (x - \frac{π}{4}) + sin (x + \frac{π}{4}) = 0

Rewrite using trig identities

cos (x - \frac{π}{4}) + sin (x + \frac{π}{4}) = 0

Rewrite using trig identities

cos (x - \frac{π}{4})

Use the Angle Difference identity:

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

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

Simplify

cos (x) cos (\frac{π}{4}) + sin (x) sin (\frac{π}{4}) : \frac{2 cos ( x ) + 2 sin ( x )}{2}

cos (x) cos (\frac{π}{4}) + sin (x) sin (\frac{π}{4})

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

cos (x) cos (\frac{π}{4})

Simplify

cos (\frac{π}{4}) : \frac{2}{2}

cos (\frac{π}{4})

Use the following trivial identity:

cos (\frac{π}{4}) = \frac{2}{2}

cos (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} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{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} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{2}{2}

= \frac{2}{2} cos (x)

Multiply fractions:

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

= \frac{2 cos ( x )}{2}

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

sin (x) sin (\frac{π}{4})

Simplify

sin (\frac{π}{4}) : \frac{2}{2}

sin (\frac{π}{4})

Use the following trivial identity:

sin (\frac{π}{4}) = \frac{2}{2}

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}

= \frac{2}{2}

= \frac{2}{2} sin (x)

Multiply fractions:

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

= \frac{2 sin ( x )}{2}

= \frac{2 cos ( x )}{2} + \frac{2 sin ( x )}{2}

Apply rule

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

= \frac{2 cos ( x ) + 2 sin ( x )}{2}

= \frac{2 cos ( x ) + 2 sin ( x )}{2}

Use the Angle Sum identity:

sin (s + t) = sin (s) cos (t) + cos (s) sin (t)

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

Simplify

sin (x) cos (\frac{π}{4}) + cos (x) sin (\frac{π}{4}) : \frac{2 sin ( x ) + 2 cos ( x )}{2}

sin (x) cos (\frac{π}{4}) + cos (x) sin (\frac{π}{4})

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

sin (x) cos (\frac{π}{4})

Simplify

cos (\frac{π}{4}) : \frac{2}{2}

cos (\frac{π}{4})

Use the following trivial identity:

cos (\frac{π}{4}) = \frac{2}{2}

cos (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} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{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} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{2}{2}

= \frac{2}{2} sin (x)

Multiply fractions:

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

= \frac{2 sin ( x )}{2}

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

cos (x) sin (\frac{π}{4})

Simplify

sin (\frac{π}{4}) : \frac{2}{2}

sin (\frac{π}{4})

Use the following trivial identity:

sin (\frac{π}{4}) = \frac{2}{2}

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}

= \frac{2}{2}

= \frac{2}{2} cos (x)

Multiply fractions:

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

= \frac{2 cos ( x )}{2}

= \frac{2 sin ( x )}{2} + \frac{2 cos ( x )}{2}

Apply rule

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

= \frac{2 sin ( x ) + 2 cos ( x )}{2}

= \frac{2 sin ( x ) + 2 cos ( x )}{2}

\frac{2 cos ( x ) + 2 sin ( x )}{2} + \frac{2 sin ( x ) + 2 cos ( x )}{2} = 0

Simplify

\frac{2 cos ( x ) + 2 sin ( x )}{2} + \frac{2 sin ( x ) + 2 cos ( x )}{2} : 2 (cos (x) + sin (x))

\frac{2 cos ( x ) + 2 sin ( x )}{2} + \frac{2 sin ( x ) + 2 cos ( x )}{2}

Apply rule

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

= \frac{2 cos ( x ) + 2 sin ( x ) + 2 sin ( x ) + 2 cos ( x )}{2}

2 cos (x) + 2 sin (x) + 2 sin (x) + 2 cos (x) = 22 cos (x) + 22 sin (x)

2 cos (x) + 2 sin (x) + 2 sin (x) + 2 cos (x)

Add similar elements:

2 cos (x) + 2 cos (x) = 22 cos (x)

= 22 cos (x) + 2 sin (x) + 2 sin (x)

Add similar elements:

2 sin (x) + 2 sin (x) = 22 sin (x)

= 22 cos (x) + 22 sin (x)

= \frac{2 2 cos ( x ) + 2 2 sin ( x )}{2}

Factor out common term

22

= \frac{2 2 ( cos ( x ) + sin ( x ) )}{2}

Divide the numbers:

\frac{2}{2} = 1

= 2 (cos (x) + sin (x))

2 (cos (x) + sin (x)) = 0

Divide both sides by

cos (x), cos (x) \neq = 0

\frac{2 ( cos ( x ) + sin ( x ) )}{cos ( x )} = \frac{0}{cos ( x )}

Simplify

2 + \frac{2 sin ( x )}{cos ( x )} = 0

Use the basic trigonometric identity:

\frac{sin ( x )}{cos ( x )} = tan (x)

2 + 2 tan (x) = 0

2 + 2 tan (x) = 0

Move

2

to the right side

2 + 2 tan (x) = 0

Subtract

2

from both sides

2 + 2 tan (x) - 2 = 0 - 2

Simplify

2 tan (x) = - 2

2 tan (x) = - 2

Divide both sides by

2

2 tan (x) = - 2

Divide both sides by

2

\frac{2 tan ( x )}{2} = \frac{- 2}{2}

Simplify

tan (x) = - 1

tan (x) = - 1

General solutions for

tan (x) = - 1

tan (x)

periodicity table with

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} tan (x) 0 \frac{3}{3} 13 \pm \infty - 3 - 1 - \frac{3}{3}

x = \frac{3 π}{4} + πn

x = \frac{3 π}{4} + πn

Graph

Popular Examples

3tan(x)+1=0

3 tan (x) + 1 = 0

cos(2x)= 7/25

cos (2 x) = \frac{7}{25}

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

sin^{2} (x) - cos^{2} (x) = cos (x)

sin(2θ)= a/5

sin (2 θ) = \frac{a}{5}

cos(a)=-1/4

cos (a) = - \frac{1}{4}

Frequently Asked Questions (FAQ)

What is the general solution for cos(x-pi/4)+sin(x+pi/4)=0 ?
The general solution for cos(x-pi/4)+sin(x+pi/4)=0 is x=(3pi)/4+pin