PROVE THE TRIGONOMETRIC IDENTITY

Prove the trig identity.

cos(A + B)/cos(A - B) = [1 - tanA*tanB]/[1 + tanA*tanB]

RHS =
[1 - tanA.tanB]/[1 + tanA.tanB]

[1 - sinA.sinB/cosA.cosB] / [1+sinA.sinB/cosA.cosB]


(cosA.cosB - sinA.sinB) (cosA.cosB + sinA.sinB)
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......... cosA.cosB ....................... cosA.cosB

(cosA.cosB - sinA.sinB) / (cosA.cosB + sinA.sinB)

cos(A+B)/cos(A-B)
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