What is the general solution for (9sin(2x)+9cos(2x))^2=81 ?

The general solution for (9sin(2x)+9cos(2x))^2=81 is x=pin+pi/2 ,x=pin+(3pi)/4 ,x=pin,x=pin+pi/4

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

Popular >

(9sin(2x)+9cos(2x))^2=81

Solution

(9 sin (2 x) + 9 cos (2 x))^{2} = 81

Solution

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

Degrees

x = 9 0^{\circ} + 18 0^{\circ} n, x = 13 5^{\circ} + 18 0^{\circ} n, x = 0^{\circ} + 18 0^{\circ} n, x = 4 5^{\circ} + 18 0^{\circ} n

Solution steps

(9 sin (2 x) + 9 cos (2 x))^{2} = 81

Subtract

81

from both sides

(9 sin (2 x) + 9 cos (2 x))^{2} - 81 = 0

Factor

(9 sin (2 x) + 9 cos (2 x))^{2} - 81 : 81 (sin (2 x) + cos (2 x) + 1) (sin (2 x) + cos (2 x) - 1)

(9 sin (2 x) + 9 cos (2 x))^{2} - 81

Rewrite

81

9^{2}

= (9 sin (2 x) + 9 cos (2 x))^{2} - 9^{2}

Apply Difference of Two Squares Formula:

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

(9 sin (2 x) + 9 cos (2 x))^{2} - 9^{2} = ((9 sin (2 x) + 9 cos (2 x)) + 9) ((9 sin (2 x) + 9 cos (2 x)) - 9)

= ((9 sin (2 x) + 9 cos (2 x)) + 9) ((9 sin (2 x) + 9 cos (2 x)) - 9)

Refine

= (9 sin (2 x) + 9 cos (2 x) + 9) (9 sin (2 x) + 9 cos (2 x) - 9)

Factor

9 sin (2 x) + 9 cos (2 x) + 9 : 9 (sin (2 x) + cos (2 x) + 1)

9 sin (2 x) + 9 cos (2 x) + 9

Factor out common term

9

= 9 (sin (2 x) + cos (2 x) + 1)

= 9 (sin (2 x) + cos (2 x) + 1) (9 sin (2 x) + 9 cos (2 x) - 9)

Factor

9 sin (2 x) + 9 cos (2 x) - 9 : 9 (sin (2 x) + cos (2 x) - 1)

9 sin (2 x) + 9 cos (2 x) - 9

Factor out common term

9

= 9 (sin (2 x) + cos (2 x) - 1)

= 9 (sin (2 x) + cos (2 x) + 1) \cdot 9 (sin (2 x) + cos (2 x) - 1)

Refine

= 81 (sin (2 x) + cos (2 x) + 1) (sin (2 x) + cos (2 x) - 1)

81 (sin (2 x) + cos (2 x) + 1) (sin (2 x) + cos (2 x) - 1) = 0

Solving each part separately

sin (2 x) + cos (2 x) + 1 = 0 or sin (2 x) + cos (2 x) - 1 = 0

sin (2 x) + cos (2 x) + 1 = 0 : x = πn + \frac{π}{2}, x = πn + \frac{3 π}{4}

sin (2 x) + cos (2 x) + 1 = 0

Rewrite using trig identities

sin (2 x) + cos (2 x) + 1

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

sin (2 x) + cos (2 x)

Rewrite as

= 2 (\frac{1}{2} sin (2 x) + \frac{1}{2} cos (2 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 (2 x) + sin (\frac{π}{4}) cos (2 x))

Use the Angle Sum identity:

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

= 2 sin (2 x + \frac{π}{4})

= 1 + 2 sin (2 x + \frac{π}{4})

1 + 2 sin (2 x + \frac{π}{4}) = 0

Move

1

to the right side

1 + 2 sin (2 x + \frac{π}{4}) = 0

Subtract

1

from both sides

1 + 2 sin (2 x + \frac{π}{4}) - 1 = 0 - 1

Simplify

2 sin (2 x + \frac{π}{4}) = - 1

2 sin (2 x + \frac{π}{4}) = - 1

Divide both sides by

2

2 sin (2 x + \frac{π}{4}) = - 1

Divide both sides by

2

\frac{2 sin ( 2 x + \frac{π}{4} )}{2} = \frac{- 1}{2}

Simplify

\frac{2 sin ( 2 x + \frac{π}{4} )}{2} = \frac{- 1}{2}

Simplify

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

\frac{2 sin ( 2 x + \frac{π}{4} )}{2}

Cancel the common factor:

2

= sin (2 x + \frac{π}{4})

Simplify

\frac{- 1}{2} : - \frac{2}{2}

\frac{- 1}{2}

Apply the fraction rule:

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

= - \frac{1}{2}

Rationalize

- \frac{1}{2} : - \frac{2}{2}

- \frac{1}{2}

Multiply by the conjugate

\frac{2}{2}

= - \frac{1 \cdot 2}{2 2}

1 \cdot 2 = 2

22 = 2

22

Apply radical rule:

a a = a

22 = 2

= 2

= - \frac{2}{2}

= - \frac{2}{2}

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

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

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

General solutions for

sin (2 x + \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}

2 x + \frac{π}{4} = \frac{5 π}{4} + 2 πn, 2 x + \frac{π}{4} = \frac{7 π}{4} + 2 πn

2 x + \frac{π}{4} = \frac{5 π}{4} + 2 πn, 2 x + \frac{π}{4} = \frac{7 π}{4} + 2 πn

Solve

2 x + \frac{π}{4} = \frac{5 π}{4} + 2 πn : x = πn + \frac{π}{2}

2 x + \frac{π}{4} = \frac{5 π}{4} + 2 πn

Move

\frac{π}{4}

to the right side

2 x + \frac{π}{4} = \frac{5 π}{4} + 2 πn

Subtract

\frac{π}{4}

from both sides

2 x + \frac{π}{4} - \frac{π}{4} = \frac{5 π}{4} + 2 πn - \frac{π}{4}

Simplify

2 x + \frac{π}{4} - \frac{π}{4} = \frac{5 π}{4} + 2 πn - \frac{π}{4}

Simplify

2 x + \frac{π}{4} - \frac{π}{4} : 2 x

2 x + \frac{π}{4} - \frac{π}{4}

Add similar elements:

\frac{π}{4} - \frac{π}{4} = 0

= 2 x

Simplify

\frac{5 π}{4} + 2 πn - \frac{π}{4} : 2 πn + π

\frac{5 π}{4} + 2 πn - \frac{π}{4}

Group like terms

= 2 πn - \frac{π}{4} + \frac{5 π}{4}

Combine the fractions

- \frac{π}{4} + \frac{5 π}{4} : π

Apply rule

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

= \frac{- π + 5 π}{4}

Add similar elements:

- π + 5 π = 4 π

= \frac{4 π}{4}

Divide the numbers:

\frac{4}{4} = 1

= π

= 2 πn + π

2 x = 2 πn + π

2 x = 2 πn + π

2 x = 2 πn + π

Divide both sides by

2

2 x = 2 πn + π

Divide both sides by

2

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

Simplify

x = πn + \frac{π}{2}

x = πn + \frac{π}{2}

Solve

2 x + \frac{π}{4} = \frac{7 π}{4} + 2 πn : x = πn + \frac{3 π}{4}

2 x + \frac{π}{4} = \frac{7 π}{4} + 2 πn

Move

\frac{π}{4}

to the right side

2 x + \frac{π}{4} = \frac{7 π}{4} + 2 πn

Subtract

\frac{π}{4}

from both sides

2 x + \frac{π}{4} - \frac{π}{4} = \frac{7 π}{4} + 2 πn - \frac{π}{4}

Simplify

2 x + \frac{π}{4} - \frac{π}{4} = \frac{7 π}{4} + 2 πn - \frac{π}{4}

Simplify

2 x + \frac{π}{4} - \frac{π}{4} : 2 x

2 x + \frac{π}{4} - \frac{π}{4}

Add similar elements:

\frac{π}{4} - \frac{π}{4} = 0

= 2 x

Simplify

\frac{7 π}{4} + 2 πn - \frac{π}{4} : 2 πn + \frac{3 π}{2}

\frac{7 π}{4} + 2 πn - \frac{π}{4}

Group like terms

= 2 πn - \frac{π}{4} + \frac{7 π}{4}

Combine the fractions

- \frac{π}{4} + \frac{7 π}{4} : \frac{3 π}{2}

Apply rule

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

= \frac{- π + 7 π}{4}

Add similar elements:

- π + 7 π = 6 π

= \frac{6 π}{4}

Cancel the common factor:

2

= \frac{3 π}{2}

= 2 πn + \frac{3 π}{2}

2 x = 2 πn + \frac{3 π}{2}

2 x = 2 πn + \frac{3 π}{2}

2 x = 2 πn + \frac{3 π}{2}

Divide both sides by

2

2 x = 2 πn + \frac{3 π}{2}

Divide both sides by

2

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

Simplify

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

Simplify

\frac{2 x}{2} : x

\frac{2 x}{2}

Divide the numbers:

\frac{2}{2} = 1

= x

Simplify

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

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

\frac{2 πn}{2} = πn

\frac{2 πn}{2}

Divide the numbers:

\frac{2}{2} = 1

= πn

\frac{\frac{3 π}{2}}{2} = \frac{3 π}{4}

\frac{\frac{3 π}{2}}{2}

Apply the fraction rule:

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

= \frac{3 π}{2 \cdot 2}

Multiply the numbers:

2 \cdot 2 = 4

= \frac{3 π}{4}

= πn + \frac{3 π}{4}

x = πn + \frac{3 π}{4}

x = πn + \frac{3 π}{4}

x = πn + \frac{3 π}{4}

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

sin (2 x) + cos (2 x) - 1 = 0 : x = πn, x = πn + \frac{π}{4}

sin (2 x) + cos (2 x) - 1 = 0

Rewrite using trig identities

sin (2 x) + cos (2 x) - 1

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

sin (2 x) + cos (2 x)

Rewrite as

= 2 (\frac{1}{2} sin (2 x) + \frac{1}{2} cos (2 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 (2 x) + sin (\frac{π}{4}) cos (2 x))

Use the Angle Sum identity:

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

= 2 sin (2 x + \frac{π}{4})

= - 1 + 2 sin (2 x + \frac{π}{4})

- 1 + 2 sin (2 x + \frac{π}{4}) = 0

Move

1

to the right side

- 1 + 2 sin (2 x + \frac{π}{4}) = 0

Add

1

to both sides

- 1 + 2 sin (2 x + \frac{π}{4}) + 1 = 0 + 1

Simplify

2 sin (2 x + \frac{π}{4}) = 1

2 sin (2 x + \frac{π}{4}) = 1

Divide both sides by

2

2 sin (2 x + \frac{π}{4}) = 1

Divide both sides by

2

\frac{2 sin ( 2 x + \frac{π}{4} )}{2} = \frac{1}{2}

Simplify

\frac{2 sin ( 2 x + \frac{π}{4} )}{2} = \frac{1}{2}

Simplify

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

\frac{2 sin ( 2 x + \frac{π}{4} )}{2}

Cancel the common factor:

2

= sin (2 x + \frac{π}{4})

Simplify

\frac{1}{2} : \frac{2}{2}

\frac{1}{2}

Multiply by the conjugate

\frac{2}{2}

= \frac{1 \cdot 2}{2 2}

1 \cdot 2 = 2

22 = 2

22

Apply radical rule:

a a = a

22 = 2

= 2

= \frac{2}{2}

sin (2 x + \frac{π}{4}) = \frac{2}{2}

sin (2 x + \frac{π}{4}) = \frac{2}{2}

sin (2 x + \frac{π}{4}) = \frac{2}{2}

General solutions for

sin (2 x + \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}

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

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

Solve

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

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

Subtract

\frac{π}{4}

from both sides

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

Simplify

2 x = 2 πn

Divide both sides by

2

2 x = 2 πn

Divide both sides by

2

\frac{2 x}{2} = \frac{2 πn}{2}

Simplify

x = πn

x = πn

Solve

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

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

Move

\frac{π}{4}

to the right side

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

Subtract

\frac{π}{4}

from both sides

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

Simplify

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

Simplify

2 x + \frac{π}{4} - \frac{π}{4} : 2 x

2 x + \frac{π}{4} - \frac{π}{4}

Add similar elements:

\frac{π}{4} - \frac{π}{4} = 0

= 2 x

Simplify

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

\frac{3 π}{4} + 2 πn - \frac{π}{4}

Group like terms

= 2 πn - \frac{π}{4} + \frac{3 π}{4}

Combine the fractions

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

Apply rule

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

= \frac{- π + 3 π}{4}

Add similar elements:

- π + 3 π = 2 π

= \frac{2 π}{4}

Cancel the common factor:

2

= \frac{π}{2}

= 2 πn + \frac{π}{2}

2 x = 2 πn + \frac{π}{2}

2 x = 2 πn + \frac{π}{2}

2 x = 2 πn + \frac{π}{2}

Divide both sides by

2

2 x = 2 πn + \frac{π}{2}

Divide both sides by

2

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

Simplify

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

Simplify

\frac{2 x}{2} : x

\frac{2 x}{2}

Divide the numbers:

\frac{2}{2} = 1

= x

Simplify

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

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

\frac{2 πn}{2} = πn

\frac{2 πn}{2}

Divide the numbers:

\frac{2}{2} = 1

= πn

\frac{\frac{π}{2}}{2} = \frac{π}{4}

\frac{\frac{π}{2}}{2}

Apply the fraction rule:

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

= \frac{π}{2 \cdot 2}

Multiply the numbers:

2 \cdot 2 = 4

= \frac{π}{4}

= πn + \frac{π}{4}

x = πn + \frac{π}{4}

x = πn + \frac{π}{4}

x = πn + \frac{π}{4}

x = πn, x = πn + \frac{π}{4}

Combine all the solutions

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

Popular Examples

-2cos^2(θ)+sin(θ)-3=-4

- 2 cos^{2} (θ) + sin (θ) - 3 = - 4

sec^2(x)-9sec(x)=0

sec^{2} (x) - 9 sec (x) = 0

-3sin(2θ)=5cos(2θ)

- 3 sin (2 θ) = 5 cos (2 θ)

(tan^2(θ)-4)(2cos(θ)+1)=0

(tan^{2} (θ) - 4) (2 cos (θ) + 1) = 0

cot(t)=-1

cot (t) = - 1

Frequently Asked Questions (FAQ)

What is the general solution for (9sin(2x)+9cos(2x))^2=81 ?
The general solution for (9sin(2x)+9cos(2x))^2=81 is x=pin+pi/2 ,x=pin+(3pi)/4 ,x=pin,x=pin+pi/4