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Asked by  | 12th Sep, 2008, 07:56: PM

Expert Answer:

this question is incorrect.

since cos(A-B) - cos(A+B) = 2 sinA sinB

so cos(π/4 +x) -cos(π/4 -x) = -2sinx sin(π/4) = -2 sinx

if it is cos(π/4 +x) + cos(π/4 -x) then it equal to 2 cos x

Answered by  | 12th Sep, 2008, 09:12: PM

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