How do you verify #cos^2 2A = (1+cos4A)/2#? Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer Bdub May 11, 2016 see below Explanation: Use Property: #cos2A=2cos^2A-1# Right Hand Side :#=(1+cos4A)/2# #=(1+cos2(2A))/2# #=(1+(2cos^2(2A)-1))/2# #=(1-1+2cos^2(2A))/2# #=(cancel1-cancel1+2cos^2(2A))/2# #=(2cos^2(2A))/2# #=(cancel2cos^2(2A))/cancel2# #=cos^2(2A)# #=# Left Hand Side 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 7992 views around the world You can reuse this answer Creative Commons License