If $ heta$ is an acute angle of a right angled triangle, then which of the following equation is **not** true?

Question

If $	heta$ is an acute angle of a right angled triangle, then which of the following equation is **not** true?

Accepted Answer

Step 1: The correct identity is $\sec^2 	heta - 	an^2 	heta = 1$, i.e., $	an^2 	heta - \sec^2 	heta = -1 
eq 1$. So option (D) is not true.

Question