What is (1+cosx)/(1+secx) for x=pi/3? Trigonometry Trigonometric Identities and Equations Proving Identities 1 Answer Shwetank Mauria Jan 2, 2017 (1+cosx)/(1+secx)=cosx and for x=pi/3, it is 1/2. Explanation: (1+cosx)/(1+secx) = (1+cosx)/(1+1/cosx) = (1+cosx)/((cosx+1)/cosx) = (1+cosx)xxcosx/(1+cosx) = cosx Hence (1+cosx)/(1+secx)=cosx for all values of x and for x=pi/3 (1+cosx)/(1+secx)=(1+cos(pi/3))/(1+sec(pi/3)) = (1+1/2)/(1+2)=(3/2)/3=3/2xx1/3=1/2 As cosx=cos(pi/3)=1/2 for x=pi/3, (1+cosx)/(1+secx)=cosx 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 1345 views around the world You can reuse this answer Creative Commons License