How do you express $cos (\frac{5 π}{6}) \cdot cos (\frac{11 π}{6})$ $cos( (5 pi)/6 ) * cos (( 11 pi) /6 )$ without using products of trigonometric functions?

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How do you express $cos (\frac{5 π}{6}) \cdot cos (\frac{11 π}{6})$ $cos( (5 pi)/6 ) * cos (( 11 pi) /6 )$ without using products of trigonometric functions?

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Answer 1 · 2016-03-18T01:01:40

$- \frac{3}{4}$ $-3/4$

Explanation:

Trig table --> $cos (\frac{5 π}{6}) = cos (π - \frac{π}{6}) = - \frac{cos π}{6} = - \frac{\sqrt{3}}{2}$ $cos ((5pi)/6) =cos(pi-pi/6)=-cospi/6=-sqrt3/2$
$cos (\frac{11 π}{6}) = cos (- \frac{π}{6} + \frac{12 π}{6}) = cos (- \frac{π}{6} + 2 π) =$ $cos ((11pi)/6) = cos (-pi/6 + (12pi)/6) = cos (-pi/6 + 2pi) =$
$cos (- \frac{π}{6}) = cos (\frac{π}{6}) = \frac{\sqrt{3}}{2}$ $cos (-pi/6) = cos (pi/6) = sqrt3/2$
The product can be expressed as:
$P = (- \frac{\sqrt{3}}{2}) (\frac{\sqrt{3}}{2}) = - \frac{3}{4}$ $P = (-sqrt3/2)(sqrt3/2) = - 3/4$

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How do you express $cos (\frac{5 π}{6}) \cdot cos (\frac{11 π}{6})$ $cos( (5 pi)/6 ) * cos (( 11 pi) /6 )$ without using products of trigonometric functions?

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How do you express cos(5π6)⋅cos(11π6)cos( (5 pi)/6 ) * cos (( 11 pi) /6 ) without using products of trigonometric functions?

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How do you express $cos (\frac{5 π}{6}) \cdot cos (\frac{11 π}{6})$ $cos( (5 pi)/6 ) * cos (( 11 pi) /6 )$ without using products of trigonometric functions?