Question #1381d Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer P dilip_k Mar 19, 2017 #RHS= (sin 5x + sin 7x)/(Cos 5x - cos 7x)# # = (2sin( (5x+7x)/2) cos ((7x-5x)/2))/ (2sin( (5x+7x)/2) sin ((7x-5x)/2))# # = (sin( 6x) cos (x))/ (sin( 6x) sin x)=cotx=LHS# 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 1025 views around the world You can reuse this answer Creative Commons License