What is the general solution for 3sin(x)=3sin(2x) ?

The general solution for 3sin(x)=3sin(2x) is x=2pin,x=pi+2pin,x= pi/3+2pin,x=(5pi)/3+2pin

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3sin(x)=3sin(2x)

Solution

3 sin (x) = 3 sin (2 x)

Solution

x = 2 πn, x = π + 2 πn, x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

Degrees

x = 0^{\circ} + 36 0^{\circ} n, x = 18 0^{\circ} + 36 0^{\circ} n, x = 6 0^{\circ} + 36 0^{\circ} n, x = 30 0^{\circ} + 36 0^{\circ} n

Solution steps

3 sin (x) = 3 sin (2 x)

Subtract

3 sin (2 x)

from both sides

3 sin (x) - 3 sin (2 x) = 0

Rewrite using trig identities

- 3 sin (2 x) + 3 sin (x)

Use the Double Angle identity:

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

= - 3 \cdot 2 sin (x) cos (x) + 3 sin (x)

Simplify

= - 6 sin (x) cos (x) + 3 sin (x)

3 sin (x) - 6 cos (x) sin (x) = 0

Factor

3 sin (x) - 6 cos (x) sin (x) : - 3 sin (x) (2 cos (x) - 1)

3 sin (x) - 6 cos (x) sin (x)

Rewrite

- 6

2 \cdot 3

= 3 sin (x) + 2 \cdot 3 sin (x) cos (x)

Factor out common term

- 3 sin (x)

= - 3 sin (x) (- 1 + 2 cos (x))

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

Solving each part separately

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

sin (x) = 0 : x = 2 πn, x = π + 2 πn

sin (x) = 0

General solutions for

sin (x) = 0

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 = 0 + 2 πn, x = π + 2 πn

x = 0 + 2 πn, x = π + 2 πn

Solve

x = 0 + 2 πn : x = 2 πn

x = 0 + 2 πn

0 + 2 πn = 2 πn

x = 2 πn

x = 2 πn, x = π + 2 πn

2 cos (x) - 1 = 0 : x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

2 cos (x) - 1 = 0

Move

1

to the right side

2 cos (x) - 1 = 0

Add

1

to both sides

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

Simplify

2 cos (x) = 1

2 cos (x) = 1

Divide both sides by

2

2 cos (x) = 1

Divide both sides by

2

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

Simplify

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

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

General solutions for

cos (x) = \frac{1}{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}

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

Combine all the solutions

x = 2 πn, x = π + 2 πn, x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

Popular Examples

sin(x)+cos(2x)=0.75

sin (x) + cos (2 x) = 0.75

sin(x)=5sin(x)+2

sin (x) = 5 sin (x) + 2

2sin^2(x)+(sqrt(3)-4)sin(x)=2sqrt(3)

2 sin^{2} (x) + (3 - 4) sin (x) = 23

4cos(30x)+12=10.5

4 cos (30 x) + 12 = 10.5

3sin^2(x)+5cos(x)=1

3 sin^{2} (x) + 5 cos (x) = 1

Frequently Asked Questions (FAQ)

What is the general solution for 3sin(x)=3sin(2x) ?
The general solution for 3sin(x)=3sin(2x) is x=2pin,x=pi+2pin,x= pi/3+2pin,x=(5pi)/3+2pin