What is the value of cos^2((4pi)/3) ?

The value of cos^2((4pi)/3) is 1/4

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

Popular >

cos^2((4pi)/3)

Solution

cos^{2} (\frac{4 π}{3})

Solution

\frac{1}{4}

Decimal Notation

0.25

Solution steps

cos^{2} (\frac{4 π}{3})

Rewrite using trig identities:

\frac{1 + cos ( \frac{2 π}{3} )}{2}

cos^{2} (\frac{4 π}{3})

Use the following identity:

cos^{2} (θ) = \frac{1 + cos ( 2 θ )}{2}

Use the Double Angle identity

cos (2 θ) = 2 cos^{2} (θ) - 1

Switch sides

2 cos^{2} (θ) - 1 = cos (2 θ)

Add

1

to both sides

2 sin^{2} (θ) = 1 + cos (2 θ)

Divide both sides by

2

cos^{2} (θ) = \frac{1 + cos ( 2 θ )}{2}

= \frac{1 + cos ( 2 \cdot \frac{4 π}{3} )}{2}

Simplify:

2 \cdot \frac{4 π}{3} = \frac{8 π}{3}

2 \cdot \frac{4 π}{3}

Multiply fractions:

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

= \frac{4 π 2}{3}

Multiply the numbers:

4 \cdot 2 = 8

= \frac{8 π}{3}

= \frac{1 + cos ( \frac{8 π}{3} )}{2}

cos (\frac{8 π}{3}) = cos (\frac{2 π}{3})

cos (\frac{8 π}{3})

Rewrite

\frac{8 π}{3}

2 π + \frac{2 π}{3}

= cos (2 π + \frac{2 π}{3})

Apply the periodicity of

cos

cos (x + 2 π) = cos (x)

cos (2 π + \frac{2 π}{3}) = cos (\frac{2 π}{3})

= cos (\frac{2 π}{3})

= \frac{1 + cos ( \frac{2 π}{3} )}{2}

= \frac{1 + cos ( \frac{2 π}{3} )}{2}

Use the following trivial identity:

cos (\frac{2 π}{3}) = - \frac{1}{2}

cos (\frac{2 π}{3})

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}

= - \frac{1}{2}

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

Simplify

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

\frac{1 - \frac{1}{2}}{2}

Join

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

1 - \frac{1}{2}

Convert element to fraction:

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

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

Since the denominators are equal, combine the fractions:

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

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

1 \cdot 2 - 1 = 1

1 \cdot 2 - 1

Multiply the numbers:

1 \cdot 2 = 2

= 2 - 1

Subtract the numbers:

2 - 1 = 1

= 1

= \frac{1}{2}

= \frac{\frac{1}{2}}{2}

Apply the fraction rule:

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

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

Multiply the numbers:

2 \cdot 2 = 4

= \frac{1}{4}

= \frac{1}{4}

Popular Examples

tan(arcsin(3/5)-arccos(-1))

tan (arcsin (\frac{3}{5}) - arccos (- 1))

((tan(0)+1)-(tan(-pi/6)+1))/(0+pi/6)

\frac{( tan ( 0 ) + 1 ) - ( tan ( - \frac{π}{6} ) + 1 )}{0 + \frac{π}{6}}

sin^2(150)

sin^{2} (15 0^{\circ})

arctan(tan((11pi)/9))

arctan (tan (\frac{11 π}{9}))

-2sin((3pi)/2)

- 2 sin (\frac{3 π}{2})

Frequently Asked Questions (FAQ)

What is the value of cos^2((4pi)/3) ?
The value of cos^2((4pi)/3) is 1/4