Question #fe77f Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer Noah G · Eddie Oct 11, 2016 Start by simplifying the left side: #sin^2theta = 16cos^4theta - 12cos^2theta + 1# #1 - cos^2theta = 16cos^4theta - 12cos^2theta + 1# #0 = 16cos^4theta - 11cos^2theta# #0 = cos^2theta(16cos^2theta - 11)# #theta = pi/2, (3pi)/2, cos^-1(+-sqrt(11)/4)# Hopefully this helps! 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 1314 views around the world You can reuse this answer Creative Commons License