What is the value of 8cos^2(30) ?

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8cos^2(30)

8 cos^{2} (3 0^{\circ})

6

Solution steps

8 cos^{2} (3 0^{\circ})

Use the following trivial identity:

cos (3 0^{\circ}) = \frac{3}{2}

cos (3 0^{\circ})

cos (x)

periodicity table with

36 0^{\circ} n

cycle:

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{3}{2}

= 8 (\frac{3}{2})^{2}

Simplify

8 (\frac{3}{2})^{2} : 6

8 (\frac{3}{2})^{2}

(\frac{3}{2})^{2} = \frac{3}{2 ^{2}}

(\frac{3}{2})^{2}

Apply exponent rule:

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

= \frac{( 3 ) ^{2}}{2 ^{2}}

(3)^{2} : 3

Apply radical rule:

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

= (3^{\frac{1}{2}})^{2}

Apply exponent rule:

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

= 3^{\frac{1}{2} \cdot 2}

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

\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

= 3

= \frac{3}{2 ^{2}}

= 8 \cdot \frac{3}{2 ^{2}}

Multiply fractions:

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

= \frac{3 \cdot 8}{2 ^{2}}

Multiply the numbers:

3 \cdot 8 = 24

= \frac{24}{2 ^{2}}

Factor

24 : 2^{3} \cdot 3

Factor

24 = 2^{3} \cdot 3

= \frac{2 ^{3} \cdot 3}{2 ^{2}}

Cancel

\frac{2 ^{3} \cdot 3}{2 ^{2}} : 2 \cdot 3

\frac{2 ^{3} \cdot 3}{2 ^{2}}

Apply exponent rule:

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

\frac{2 ^{3}}{2 ^{2}} = 2^{3 - 2}

= 3 \cdot 2^{3 - 2}

Subtract the numbers:

3 - 2 = 1

= 2 \cdot 3

= 2 \cdot 3

Multiply the numbers:

2 \cdot 3 = 6

= 6

= 6

cos (2 arccos (- 0.5))

sin (π + i \frac{π}{2})

arcsin (\frac{sin ( 4 5 ^{\circ} )}{1.41})

5 sin (5 3^{\circ})

arccos (\frac{1}{14})