Question

Find the correct trigonometric identity.

(a) cos^2 θ = 1 – sin^2 θ

(b) cos^2 θ = 1 + sin^2 θ

(c) tan^2 θ + sec^2 θ = 1

(d) tan^2 θ = sec^2 θ + 1

This question was posed to me in final exam.

This key question is from Trigonometric Identities in section Trigonometry of Mathematics – Class 10

Answer 1

Correct answer is (a) cos^2 θ = 1 – sin^2 θ

The explanation is: The appropriate trigonometric identity used here is sin^2 θ + cos^2 θ = 1.

cos^2 θ = 1 – sin^2 θ