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

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

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Popular >

sin^3(x)=cos^3(x)

Solution

sin^{3} (x) = cos^{3} (x)

Solution

x = \frac{π}{4} + πn

Degrees

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

Solution steps

sin^{3} (x) = cos^{3} (x)

Subtract

cos^{3} (x)

from both sides

sin^{3} (x) - cos^{3} (x) = 0

Factor

sin^{3} (x) - cos^{3} (x) : (sin (x) - cos (x)) (sin^{2} (x) + sin (x) cos (x) + cos^{2} (x))

sin^{3} (x) - cos^{3} (x)

Apply Difference of Cubes Formula:

x^{3} - y^{3} = (x - y) (x^{2} + x y + y^{2})

sin^{3} (x) - cos^{3} (x) = (sin (x) - cos (x)) (sin^{2} (x) + sin (x) cos (x) + cos^{2} (x))

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

(sin (x) - cos (x)) (sin^{2} (x) + sin (x) cos (x) + cos^{2} (x)) = 0

Rewrite using trig identities

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

Use the Pythagorean identity:

cos^{2} (x) + sin^{2} (x) = 1

= (- cos (x) + sin (x)) (cos (x) sin (x) + 1)

(- cos (x) + sin (x)) (cos (x) sin (x) + 1) = 0

Solving each part separately

- cos (x) + sin (x) = 0 or cos (x) sin (x) + 1 = 0

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

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

Rewrite using trig identities

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

Divide both sides by

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

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

Simplify

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

Use the basic trigonometric identity:

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

- 1 + tan (x) = 0

- 1 + tan (x) = 0

Move

1

to the right side

- 1 + tan (x) = 0

Add

1

to both sides

- 1 + tan (x) + 1 = 0 + 1

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{π}{4} + πn

x = \frac{π}{4} + πn

cos (x) sin (x) + 1 = 0 :

No Solution

cos (x) sin (x) + 1 = 0

Rewrite using trig identities

cos (x) sin (x) + 1

Use the Double Angle identity:

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

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

= 1 + \frac{sin ( 2 x )}{2}

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

Move

1

to the right side

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

Subtract

1

from both sides

1 + \frac{sin ( 2 x )}{2} - 1 = 0 - 1

Simplify

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

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

Multiply both sides by

2

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

Multiply both sides by

2

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

Simplify

sin (2 x) = - 2

sin (2 x) = - 2

- 1 \leq sin (x) \leq 1

No Solution

Combine all the solutions

x = \frac{π}{4} + πn

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sec(x)sin(x)+cos(x)=sec(x)

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Frequently Asked Questions (FAQ)

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