Question #7218e Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer Bdub Apr 16, 2016 See below Explanation: LHS=left hand side, RHS =right hand side LHS=#(sin(2x+x))/(1+2cos2x)# #=(sin2xcosx+cos2xsinx)/(1+2cos2x)# #=((2sinxcosx)cosx+(1-2sin^2x)sinx)/(1+2cos2x)# #=(2sinxcos^2x+sinx-2sin^3x)/(1+2(1-2sin^2x))# #=(2sinx(1-sin^2x)+sinx-2sin^3x)/(1+2-4sin^2x)# #=(2sinx-2sin^3x+sinx-2sin^3x)/(3-4sin^2x)# #=(3sinx-4sin^3x)/(3-4sin^2x)# #=(sinx(3-4sin^2x))/(3-4sin^2x)# #=sinx# #=RHS# 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 1821 views around the world You can reuse this answer Creative Commons License