What is the general solution for cos(3y)=-1/(sqrt(2)) ?

The general solution for cos(3y)=-1/(sqrt(2)) is y= pi/4+(2pin)/3 ,y=(5pi}{12}+\frac{2pin)/3

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cos(3y)=-1/(sqrt(2))

Solution

cos (3 y) = - \frac{1}{2}

Solution

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

Radians

y = \frac{π}{4} + \frac{2 π}{3} n, y = \frac{5 π}{12} + \frac{2 π}{3} n

Solution steps

cos (3 y) = - \frac{1}{2}

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}

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

General solutions for

cos (3 y) = - \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 y = \frac{3 π}{4} + 2 πn, 3 y = \frac{5 π}{4} + 2 πn

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

Solve

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

3 y = \frac{3 π}{4} + 2 πn

Divide both sides by

3

3 y = \frac{3 π}{4} + 2 πn

Divide both sides by

3

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

Simplify

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

Simplify

\frac{3 y}{3} : y

\frac{3 y}{3}

Divide the numbers:

\frac{3}{3} = 1

= y

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}

y = \frac{π}{4} + \frac{2 πn}{3}

y = \frac{π}{4} + \frac{2 πn}{3}

y = \frac{π}{4} + \frac{2 πn}{3}

Solve

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

3 y = \frac{5 π}{4} + 2 πn

Divide both sides by

3

3 y = \frac{5 π}{4} + 2 πn

Divide both sides by

3

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

Simplify

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

Simplify

\frac{3 y}{3} : y

\frac{3 y}{3}

Divide the numbers:

\frac{3}{3} = 1

= y

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}

y = \frac{5 π}{12} + \frac{2 πn}{3}

y = \frac{5 π}{12} + \frac{2 πn}{3}

y = \frac{5 π}{12} + \frac{2 πn}{3}

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

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Frequently Asked Questions (FAQ)

What is the general solution for cos(3y)=-1/(sqrt(2)) ?
The general solution for cos(3y)=-1/(sqrt(2)) is y= pi/4+(2pin)/3 ,y=(5pi}{12}+\frac{2pin)/3