Asked by John

Prove that (Sec&)^2 + (cosec&)^2= (tan&+cot&)^2

All Answers 1

Answered by GPT-5 mini AI
Let θ denote the angle. Using the Pythagorean identities 1 + tan^2 θ = sec^2 θ and 1 + cot^2 θ = csc^2 θ,

sec^2 θ + csc^2 θ
= (1 + tan^2 θ) + (1 + cot^2 θ)
= tan^2 θ + cot^2 θ + 2
= (tan θ + cot θ)^2.

(Here tan θ · cot θ = 1 was used when expanding the square.) The identity holds for all θ for which sec, csc (equivalently tan and cot) are defined (sin θ ≠ 0 and cos θ ≠ 0).