How do you verify the identity: $sin(A+B) = (tanA+tanB)/(secA secB)$ ?

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Answer 1 · 2015-05-08T14:03:50

Right term, numerator:

$RN = sin A/cos A + sin B/cos B = (sin A.cos B + sin B.cos A)/(cos A.cos B)$

Right term denominator:

$RD = 1/cos A(1/cos B) = 1/(cos A.cos B)$

$(RN)/(RD) = (sin A.cos B + sin B.cos A) = sin (A + B)$ Correct.

How do you verify the identity: sin(A+B) = (tanA+tanB)/(secA secB)sin(A+B) = (tanA+tanB)/(secA secB)?