Question #b1a65 Trigonometry Trigonometric Identities and Equations Double Angle Identities 1 Answer Douglas K. Apr 23, 2017 cos(cos−1(3π))=3π, because any function f(f−1(x))=x Answer link Related questions What are Double Angle Identities? How do you use a double angle identity to find the exact value of each expression? How do you use a double-angle identity to find the exact value of sin 120°? How do you use double angle identities to solve equations? How do you find all solutions for sin2x=cosx for the interval [0,2π]? How do you find all solutions for 4sinθcosθ=√3 for the interval [0,2π]? How do you simplify cosx(2sinx+cosx)−sin2x? If tanx=0.3, then how do you find tan 2x? If sinx=53, what is the sin 2x equal to? How do you prove cos2A=2cos2A−1? See all questions in Double Angle Identities Impact of this question 1514 views around the world You can reuse this answer Creative Commons License