How do you verify #sin^2 theta cos ^2 theta = 1/8 [1-cos(4 theta)]#? Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer Nghi N. May 25, 2015 Use trig identities: #2sin a.cos a = sin 2a# and # 2sin^2 a = 1 - cos 2a# #sin^2 a.cos^2 a # = #(1/4)(sin^2 2a)# = #(1/8)(2sin^2 2a)# = #= (1/8)(1 - cos 4a)# 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 11123 views around the world You can reuse this answer Creative Commons License