How do you verify cos4x−sin4x=cos2x−sin2x? Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer Kazi Ashiq Iqbal Nov 15, 2015 cos4x - sin4x (cos2x)2−(sin2)2 (cos2x+sin2x)(cos2x−sin2x) --applying the formula of a2−b2 1×(cos2x−sin2x) --- since cos2x+sin2x =1 cos2x−sin2x Answer link Related questions What does it mean to prove a trigonometric identity? How do you prove cscθ×tanθ=secθ? How do you prove (1−cos2x)(1+cot2x)=1? How do you show that 2sinxcosx=sin2x? is true for 5π6? How do you prove that secxcotx=cscx? How do you prove that cos2x(1+tan2x)=1? How do you prove that 2sinxsecx(cos4x−sin4x)=tan2x? How do you verify the identity: −cotx=sin3x+sinxcos3x−cosx? How do you prove that tanx+cosx1+sinx=secx? How do you prove the identity sinx−cosxsinx+cosx=2sin2x−11+2sinxcosx? See all questions in Proving Identities Impact of this question 1656 views around the world You can reuse this answer Creative Commons License