How do you express $cos (\frac{5 π}{4}) \cdot cos (\frac{5 π}{3})$ $cos( (5 pi)/4 ) * cos (( 5 pi) /3 )$ without using products of trigonometric functions?

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How do you express $cos (\frac{5 π}{4}) \cdot cos (\frac{5 π}{3})$ $cos( (5 pi)/4 ) * cos (( 5 pi) /3 )$ without using products of trigonometric functions?

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Answer 1 · 2016-02-15T05:39:32

$- \frac{\sqrt{2}}{4}$ $-sqrt2/4$

Explanation:

$cos (\frac{5 π}{4}) = cos (\frac{π}{4} + π) = - \frac{cos π}{4} = - \frac{\sqrt{2}}{2}$ $cos ((5pi)/4) = cos (pi/4 + pi) = - cos pi/4 = -sqrt2/2$
$cos (\frac{5 π}{3}) = cos (\frac{2 π}{3} + π) = - cos (\frac{2 π}{3}) = \frac{1}{2}$ $cos ((5pi)/3) = cos ((2pi)/3 + pi) = - cos ((2pi)/3) = 1/2$

Product $cos (\frac{5 π}{4}) cos (\frac{5 π}{3}) = - (\frac{\sqrt{2}}{2}) (\frac{1}{2}) = - \frac{\sqrt{2}}{4}$ $cos((5pi)/4)cos ((5pi)/3) = -(sqrt2/2)(1/2) = -sqrt2/4$

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How do you express $cos (\frac{5 π}{4}) \cdot cos (\frac{5 π}{3})$ $cos( (5 pi)/4 ) * cos (( 5 pi) /3 )$ without using products of trigonometric functions?

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Explanation:

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How do you express cos( (5 pi)/4 ) * cos (( 5 pi) /3 ) cos(5π4)⋅cos(5π3)cos( (5 pi)/4 ) * cos (( 5 pi) /3 ) without using products of trigonometric functions?

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How do you express $cos (\frac{5 π}{4}) \cdot cos (\frac{5 π}{3})$ $cos( (5 pi)/4 ) * cos (( 5 pi) /3 )$ without using products of trigonometric functions?