Question #5df8b Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer P dilip_k Dec 21, 2016 GIVEN tan(A+B)tan(A−B)=λ ⇒sin(A+B)cos(A−B)sin(A−B)cos(A+B)=λ By dividendo and componendo ⇒(sin(A+B)cos(A−B))−(sin(A−B)cos(A+B))(sin(A+B)cos(A−B))+(sin(A−B)cos(A+B))=λ−1λ+1 ⇒sin(A+B−A+B)sin(A+B+A−B)=λ−1λ+1 ⇒sin(2B)sin(2A)=λ−1λ+1 Proved Answer link Related questions What does it mean to prove a trigonometric identity? How do you prove cscθ×tanθ=secθ? How do you prove (1−cos2x)(1+cot2x)=1? How do you show that 2sinxcosx=sin2x? is true for 5π6? How do you prove that secxcotx=cscx? How do you prove that cos2x(1+tan2x)=1? How do you prove that 2sinxsecx(cos4x−sin4x)=tan2x? How do you verify the identity: −cotx=sin3x+sinxcos3x−cosx? How do you prove that tanx+cosx1+sinx=secx? How do you prove the identity sinx−cosxsinx+cosx=2sin2x−11+2sinxcosx? See all questions in Proving Identities Impact of this question 2313 views around the world You can reuse this answer Creative Commons License