Question #628c9 Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer Konstantinos Michailidis Mar 29, 2016 We have that (1+cosA)(1-CosA)(1+Cot^2A)= (1-cos^2 A)*(1+cos^2 A/sin^2 A)= (sin^2 A)*((sin^2 A+cos^2 A)/(sin^2 A))= (sin^2 A)*(1/(sin^2 A))=1 Footnote We used the identities sin^2A+cos^2A=1 2.cotA=cosA/sinA 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 1732 views around the world You can reuse this answer Creative Commons License