How do you verify the identity: #sin(A+B) = (tanA+tanB)/(secA secB)#? Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer Nghi N. May 8, 2015 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. Answer link Related questions What does it mean to prove a trigonometric identity? How do you prove #\csc \theta \times \tan \theta = \sec \theta#? How do you prove #(1-\cos^2 x)(1+\cot^2 x) = 1#? How do you show that #2 \sin x \cos x = \sin 2x#? is true for #(5pi)/6#? How do you prove that #sec xcot x = csc x#? How do you prove that #cos 2x(1 + tan 2x) = 1#? How do you prove that #(2sinx)/[secx(cos4x-sin4x)]=tan2x#? How do you verify the identity: #-cotx =(sin3x+sinx)/(cos3x-cosx)#? How do you prove that #(tanx+cosx)/(1+sinx)=secx#? How do you prove the identity #(sinx - cosx)/(sinx + cosx) = (2sin^2x-1)/(1+2sinxcosx)#? See all questions in Proving Identities Impact of this question 5344 views around the world You can reuse this answer Creative Commons License