AM-2545

Basic trigonometric identities

A Math · Secondary 4 · Medium · Basic trigonometric identities

1. The identity is true because $\sec^2x-\tan^2x=1$ after simplifying to $\dfrac{\cos^2x}{\cos^2x}$.
2. The identity is false because $\sec^2x-\tan^2x=\dfrac{1}{\sin^2x}$.
3. The identity is false because $\sec^2x-\tan^2x=\cos^2x$.
4. The identity is true only when $x=0$.

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