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Popular Trigonometry >

solvefor y,v=(1-4cos(5y))^{-1/2}

Solution

solve for

y, v = (1 - 4 cos (5 y))^{- \frac{1}{2}}

Solution

y = \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}, y = - \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

Solution steps

v = (1 - 4 cos (5 y))^{- \frac{1}{2}}

Switch sides

(1 - 4 cos (5 y))^{- \frac{1}{2}} = v

Take both sides of the equation to the power of

- 2 : 1 - 4 cos (5 y) = \frac{1}{v ^{2}}

(1 - 4 cos (5 y))^{- \frac{1}{2}} = v

((1 - 4 cos (5 y))^{- \frac{1}{2}})^{- 2} = v^{- 2}

Expand

((1 - 4 cos (5 y))^{- \frac{1}{2}})^{- 2} : 1 - 4 cos (5 y)

((1 - 4 cos (5 y))^{- \frac{1}{2}})^{- 2}

Apply exponent rule:

a^{- b} = \frac{1}{a ^{b}}

= \frac{1}{( ( 1 - 4 cos ( 5 y ) ) ^{- \frac{1}{2}} ) ^{2}}

((1 - 4 cos (5 y))^{- \frac{1}{2}})^{2} : (1 - 4 cos (5 y))^{- 1}

Apply exponent rule:

(a^{b})^{c} = a^{b c}

= (1 - 4 cos (5 y))^{(- \frac{1}{2}) \cdot 2}

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

(- \frac{1}{2}) \cdot 2

Remove parentheses:

(- a) = - a

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

Multiply fractions:

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

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

Cancel the common factor:

2

= - 1

= (1 - 4 cos (5 y))^{- 1}

= \frac{1}{( 1 - 4 cos ( 5 y ) ) ^{- 1}}

Apply exponent rule:

a^{- 1} = \frac{1}{a}

(1 - 4 cos (5 y))^{- 1} = \frac{1}{( 1 - 4 cos ( 5 y ) )}

= \frac{1}{\frac{1}{1 - 4 c o s ( 5 y )}}

Apply the fraction rule:

\frac{1}{\frac{b}{c}} = \frac{c}{b}

= \frac{1 - 4 cos ( 5 y )}{1}

Apply the fraction rule:

\frac{a}{1} = a

= 1 - 4 cos (5 y)

Refine

= 1 - 4 cos (5 y)

Expand

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

v^{- 2}

Apply exponent rule:

a^{- b} = \frac{1}{a ^{b}}

= \frac{1}{v ^{2}}

1 - 4 cos (5 y) = \frac{1}{v ^{2}}

1 - 4 cos (5 y) = \frac{1}{v ^{2}}

Solve

1 - 4 cos (5 y) = \frac{1}{v ^{2}} : cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}}

1 - 4 cos (5 y) = \frac{1}{v ^{2}}

Move

1

to the right side

1 - 4 cos (5 y) = \frac{1}{v ^{2}}

Subtract

1

from both sides

1 - 4 cos (5 y) - 1 = \frac{1}{v ^{2}} - 1

Simplify

- 4 cos (5 y) = \frac{1}{v ^{2}} - 1

- 4 cos (5 y) = \frac{1}{v ^{2}} - 1

Divide both sides by

- 4

- 4 cos (5 y) = \frac{1}{v ^{2}} - 1

Divide both sides by

- 4

\frac{- 4 cos ( 5 y )}{- 4} = \frac{\frac{1}{v ^{2}}}{- 4} - \frac{1}{- 4}

Simplify

\frac{- 4 cos ( 5 y )}{- 4} = \frac{\frac{1}{v ^{2}}}{- 4} - \frac{1}{- 4}

Simplify

\frac{- 4 cos ( 5 y )}{- 4} : cos (5 y)

\frac{- 4 cos ( 5 y )}{- 4}

Apply the fraction rule:

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

= \frac{4 cos ( 5 y )}{4}

Divide the numbers:

\frac{4}{4} = 1

= cos (5 y)

Simplify

\frac{\frac{1}{v ^{2}}}{- 4} - \frac{1}{- 4} : - \frac{1 - v ^{2}}{4 v ^{2}}

\frac{\frac{1}{v ^{2}}}{- 4} - \frac{1}{- 4}

Apply rule

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

= \frac{\frac{1}{v ^{2}} - 1}{- 4}

Apply the fraction rule:

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

= - \frac{\frac{1}{v ^{2}} - 1}{4}

Join

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

\frac{1}{v ^{2}} - 1

Convert element to fraction:

1 = \frac{1 v ^{2}}{v ^{2}}

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

Since the denominators are equal, combine the fractions:

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

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

Multiply:

1 \cdot v^{2} = v^{2}

= \frac{1 - v ^{2}}{v ^{2}}

= - \frac{\frac{- v ^{2} + 1}{v ^{2}}}{4}

Apply the fraction rule:

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

= - \frac{- v ^{2} + 1}{4 v ^{2}}

cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}}

cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}}

cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}}

cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}}

Verify Solutions:

cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}} {v < 0 or v > 0}

Check the solutions by plugging them into

(1 - 4 cos (5 y))^{- \frac{1}{2}} = v

Remove the ones that don't agree with the equation.

Plug

cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}} : (1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}} = v \Rightarrow v < 0 or v > 0

(1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}} = v

Take both sides of the equation to the power of

- 2 : \frac{1}{v ^{2}} = \frac{1}{v ^{2}}

(1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}} = v

((1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}})^{- 2} = v^{- 2}

Expand

((1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}})^{- 2} : \frac{1}{v ^{2}}

((1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}})^{- 2}

Apply exponent rule:

a^{- b} = \frac{1}{a ^{b}}

= \frac{1}{( ( 1 - 4 ( - \frac{1 - v ^{2}}{4 v ^{2}} ) ) ^{- \frac{1}{2}} ) ^{2}}

((1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}})^{2} : (1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- 1}

Apply exponent rule:

(a^{b})^{c} = a^{b c}

= (1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{(- \frac{1}{2}) \cdot 2}

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

(- \frac{1}{2}) \cdot 2

Remove parentheses:

(- a) = - a

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

Multiply fractions:

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

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

Cancel the common factor:

2

= - 1

= (1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- 1}

= \frac{1}{( 1 - 4 ( - \frac{1 - v ^{2}}{4 v ^{2}} ) ) ^{- 1}}

Apply exponent rule:

a^{- 1} = \frac{1}{a}

(1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- 1} = \frac{1}{( 1 - 4 ( - \frac{1 - v ^{2}}{4 v ^{2}} ) )}

= \frac{1}{\frac{1}{1 - 4 ( - \frac{1 - v ^{2}}{4 v ^{2}} )}}

Apply the fraction rule:

\frac{1}{\frac{b}{c}} = \frac{c}{b}

= \frac{1 - 4 ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{1}

Apply the fraction rule:

\frac{a}{1} = a

= 1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}})

Expand

1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}) : \frac{1}{v ^{2}}

(1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))

Apply rule

- (- a) = a

= 1 + 4 \cdot \frac{1 - v ^{2}}{4 v ^{2}}

4 \cdot \frac{1 - v ^{2}}{4 v ^{2}} = \frac{1 - v ^{2}}{v ^{2}}

4 \cdot \frac{1 - v ^{2}}{4 v ^{2}}

Multiply fractions:

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

= \frac{( 1 - v ^{2} ) \cdot 4}{4 v ^{2}}

Cancel the common factor:

4

= \frac{1 - v ^{2}}{v ^{2}}

= 1 + \frac{- v ^{2} + 1}{v ^{2}}

Apply the fraction rule:

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

\frac{1 - v ^{2}}{v ^{2}} = \frac{1}{v ^{2}} - \frac{v ^{2}}{v ^{2}}

= 1 + \frac{1}{v ^{2}} - \frac{v ^{2}}{v ^{2}}

Apply rule

\frac{a}{a} = 1

\frac{v ^{2}}{v ^{2}} = 1

= 1 + \frac{1}{v ^{2}} - 1

Group like terms

= \frac{1}{v ^{2}} + 1 - 1

1 - 1 = 0

= \frac{1}{v ^{2}}

= \frac{1}{v ^{2}}

Expand

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

v^{- 2}

Apply exponent rule:

a^{- b} = \frac{1}{a ^{b}}

= \frac{1}{v ^{2}}

\frac{1}{v ^{2}} = \frac{1}{v ^{2}}

\frac{1}{v ^{2}} = \frac{1}{v ^{2}}

Solve

\frac{1}{v ^{2}} = \frac{1}{v ^{2}} :

True for all

v

\frac{1}{v ^{2}} = \frac{1}{v ^{2}}

Subtract

\frac{1}{v ^{2}}

from both sides

\frac{1}{v ^{2}} - \frac{1}{v ^{2}} = \frac{1}{v ^{2}} - \frac{1}{v ^{2}}

Simplify

0 = 0

Both sides are equal

True for all v

Verify Solutions

Find undefined (singularity) points:

v = 0

Take the denominator(s) of

\frac{1}{v ^{2}}

and compare to zero

Solve

v^{2} = 0 : v = 0

v^{2} = 0

Apply rule

x^{n} = 0 \Rightarrow x = 0

v = 0

Take the denominator(s) of

\frac{1}{v ^{2}}

and compare to zero

Solve

v^{2} = 0 : v = 0

v^{2} = 0

Apply rule

x^{n} = 0 \Rightarrow x = 0

v = 0

The following points are undefined

v = 0

Since the equation is undefined for:

0

True for all v

True for all v

Verify Solutions:

v < 0 or v > 0

(1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}} = v

Domain of

(1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}} : v < 0 or v > 0

Domain definition

Find undefined (singularity) points:

v = 0

(1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}}

Take the denominator(s) of

(1 - 4 (- \frac{1 - v ^{2}}{4 v ^{2}}))^{- \frac{1}{2}}

and compare to zero

v = 0

The following points are undefined

v = 0

The function domain

v < 0 or v > 0

Combine domain interval with solution interval:

True for all v and (v < 0 or v > 0)

Merge Overlapping Intervals

v < 0 or v > 0

The solution is

v < 0 or v > 0

The solution is

cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}} {v < 0 or v > 0}

Apply trig inverse properties

cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}}

General solutions for

cos (5 y) = - \frac{1 - v ^{2}}{4 v ^{2}}

cos (x) = a \Rightarrow x = arccos (a) + 2 πn, x = - arccos (a) + 2 πn

5 y = arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn, 5 y = - arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn

5 y = arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn, 5 y = - arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn

Solve

5 y = arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn : y = \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

5 y = arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn

Divide both sides by

5

5 y = arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn

Divide both sides by

5

\frac{5 y}{5} = \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

Simplify

y = \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

y = \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

Solve

5 y = - arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn : y = - \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

5 y = - arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn

Divide both sides by

5

5 y = - arccos (- \frac{1 - v ^{2}}{4 v ^{2}}) + 2 πn

Divide both sides by

5

\frac{5 y}{5} = - \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

Simplify

y = - \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

y = - \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

y = \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}, y = - \frac{arccos ( - \frac{1 - v ^{2}}{4 v ^{2}} )}{5} + \frac{2 πn}{5}

Graph

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