Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 1 - No. 36)
Which of the following identities is correct?
sin^2(x) + cos^2(x) = 0
sin^2(x) + cos^2(x) = 2
sin^2(x) + cos^2(x) = 1
sin^2(x) + cos^2(x) = -1
Explicação
This is a fundamental trigonometric identity.