What is the general solution for 2cos(3θ)=-sqrt(2) ?

The general solution for 2cos(3θ)=-sqrt(2) is θ= pi/4+(2pin)/3 ,θ=(5pi}{12}+\frac{2pin)/3

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2cos(3θ)=-sqrt(2)

Solution

2 cos (3 θ) = - 2

Solution

θ = \frac{π}{4} + \frac{2 πn}{3}, θ = \frac{5 π}{12} + \frac{2 πn}{3}

Degrees

θ = 4 5^{\circ} + 12 0^{\circ} n, θ = 7 5^{\circ} + 12 0^{\circ} n

Solution steps

2 cos (3 θ) = - 2

Divide both sides by

2

2 cos (3 θ) = - 2

Divide both sides by

2

\frac{2 cos ( 3 θ )}{2} = \frac{- 2}{2}

Simplify

cos (3 θ) = - \frac{2}{2}

cos (3 θ) = - \frac{2}{2}

General solutions for

cos (3 θ) = - \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}

3 θ = \frac{3 π}{4} + 2 πn, 3 θ = \frac{5 π}{4} + 2 πn

3 θ = \frac{3 π}{4} + 2 πn, 3 θ = \frac{5 π}{4} + 2 πn

Solve

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

3 θ = \frac{3 π}{4} + 2 πn

Divide both sides by

3

3 θ = \frac{3 π}{4} + 2 πn

Divide both sides by

3

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

Simplify

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

Simplify

\frac{3 θ}{3} : θ

\frac{3 θ}{3}

Divide the numbers:

\frac{3}{3} = 1

= θ

Simplify

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

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

\frac{\frac{3 π}{4}}{3} = \frac{π}{4}

\frac{\frac{3 π}{4}}{3}

Apply the fraction rule:

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

= \frac{3 π}{4 \cdot 3}

Multiply the numbers:

4 \cdot 3 = 12

= \frac{3 π}{12}

Cancel the common factor:

3

= \frac{π}{4}

= \frac{π}{4} + \frac{2 πn}{3}

θ = \frac{π}{4} + \frac{2 πn}{3}

θ = \frac{π}{4} + \frac{2 πn}{3}

θ = \frac{π}{4} + \frac{2 πn}{3}

Solve

3 θ = \frac{5 π}{4} + 2 πn : θ = \frac{5 π}{12} + \frac{2 πn}{3}

3 θ = \frac{5 π}{4} + 2 πn

Divide both sides by

3

3 θ = \frac{5 π}{4} + 2 πn

Divide both sides by

3

\frac{3 θ}{3} = \frac{\frac{5 π}{4}}{3} + \frac{2 πn}{3}

Simplify

\frac{3 θ}{3} = \frac{\frac{5 π}{4}}{3} + \frac{2 πn}{3}

Simplify

\frac{3 θ}{3} : θ

\frac{3 θ}{3}

Divide the numbers:

\frac{3}{3} = 1

= θ

Simplify

\frac{\frac{5 π}{4}}{3} + \frac{2 πn}{3} : \frac{5 π}{12} + \frac{2 πn}{3}

\frac{\frac{5 π}{4}}{3} + \frac{2 πn}{3}

\frac{\frac{5 π}{4}}{3} = \frac{5 π}{12}

\frac{\frac{5 π}{4}}{3}

Apply the fraction rule:

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

= \frac{5 π}{4 \cdot 3}

Multiply the numbers:

4 \cdot 3 = 12

= \frac{5 π}{12}

= \frac{5 π}{12} + \frac{2 πn}{3}

θ = \frac{5 π}{12} + \frac{2 πn}{3}

θ = \frac{5 π}{12} + \frac{2 πn}{3}

θ = \frac{5 π}{12} + \frac{2 πn}{3}

θ = \frac{π}{4} + \frac{2 πn}{3}, θ = \frac{5 π}{12} + \frac{2 πn}{3}

Popular Examples

cos(θ)=2sin(θ)

cos (θ) = 2 sin (θ)

12sin^2(θ)-3=0

12 sin^{2} (θ) - 3 = 0

sqrt(2)sin^2(θ)+sin(θ)=0

2 sin^{2} (θ) + sin (θ) = 0

tan^2(x)=1-sec^2(x)

tan^{2} (x) = 1 - sec^{2} (x)

sec(x)=cos(x)

sec (x) = cos (x)

Frequently Asked Questions (FAQ)

What is the general solution for 2cos(3θ)=-sqrt(2) ?
The general solution for 2cos(3θ)=-sqrt(2) is θ= pi/4+(2pin)/3 ,θ=(5pi}{12}+\frac{2pin)/3