What is the general solution for sin^2(3x)+2sin(x)cos(x)+cos^2(3x)=0 ?

The general solution for sin^2(3x)+2sin(x)cos(x)+cos^2(3x)=0 is x=(3pi)/4+pin

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sin^2(3x)+2sin(x)cos(x)+cos^2(3x)=0

sin^{2} (3 x) + 2 sin (x) cos (x) + cos^{2} (3 x) = 0

x = \frac{3 π}{4} + πn

Degrees

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

Solution steps

sin^{2} (3 x) + 2 sin (x) cos (x) + cos^{2} (3 x) = 0

Rewrite using trig identities

2 cos (x) sin (x) + 1

Use the Double Angle identity:

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

= 1 + sin (2 x)

1 + sin (2 x) = 0

Move

1

to the right side

1 + sin (2 x) = 0

Subtract

1

from both sides

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

Simplify

sin (2 x) = - 1

sin (2 x) = - 1

General solutions for

sin (2 x) = - 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}

2 x = \frac{3 π}{2} + 2 πn

2 x = \frac{3 π}{2} + 2 πn

Solve

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

2 x = \frac{3 π}{2} + 2 πn

Divide both sides by

2

2 x = \frac{3 π}{2} + 2 πn

Divide both sides by

2

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

Simplify

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

Simplify

\frac{2 x}{2} : x

\frac{2 x}{2}

Divide the numbers:

\frac{2}{2} = 1

= x

Simplify

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

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

\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}

\frac{2 πn}{2} = πn

\frac{2 πn}{2}

Divide the numbers:

\frac{2}{2} = 1

= πn

= \frac{3 π}{4} + πn

x = \frac{3 π}{4} + πn

x = \frac{3 π}{4} + πn

x = \frac{3 π}{4} + πn

x = \frac{3 π}{4} + πn

20 sin (t) cos (t) = - 4 sin (t)

cos (x) - cos (2 x) = 0, 0^{\circ} \leq x < 36 0^{\circ}

3 = - 3 cos (θ)

2 cos (θ) - 3 = 0, 0 \leq θ \leq 2 π

- 4 sin (x) = cos^{2} (x) + 1, 0 \leq x \leq 2 π

What is the general solution for sin^2(3x)+2sin(x)cos(x)+cos^2(3x)=0 ?
The general solution for sin^2(3x)+2sin(x)cos(x)+cos^2(3x)=0 is x=(3pi)/4+pin