If $2 cos A cos B = cos (x) + cos (y)$ $2cosAcosB=cos(x)+cos(y)$ , then $x + y =$ $x+y=$ ??

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If $2 cos A cos B = cos (x) + cos (y)$ $2cosAcosB=cos(x)+cos(y)$ , then $x + y =$ $x+y=$ ??

1 Answer

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Answer 1 · 2016-09-16T14:09:50

2A

Explanation:

cos x + cos y = 2cos A.cos B (1)
Use trig identity:
$cos x + cos y = 2 cos (\frac{x + y}{2}) . cos (\frac{x - y}{2})$ $cos x + cos y = 2cos ((x + y)/2).cos ((x - y)/2)$ (2)
Compare (1) and (2), we get:
$A = \frac{x + y}{2}$ $A = (x + y)/2$
$(x + y) = 2 A$ $(x + y) = 2A$

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If $2 cos A cos B = cos (x) + cos (y)$ $2cosAcosB=cos(x)+cos(y)$ , then $x + y =$ $x+y=$ ??

1 Answer

Explanation:

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If 2cosAcosB=cos(x)+cos(y)2cosAcosB=cos(x)+cos(y)2cosAcosB=cos(x)+cos(y), then x+y=x+y=x+y=??

1 Answer

Explanation:

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If $2 cos A cos B = cos (x) + cos (y)$ $2cosAcosB=cos(x)+cos(y)$ , then $x + y =$ $x+y=$ ??