alleryWhich of the following is true?
A$\tan 90^\circ=1$
B$\sec 90^\circ=1$
C$\cot 90^\circ=0$
D$\csc 0^\circ=0$
Answer & Solution
Correct answer: C. $\cot 90^\circ=0$
From the standard trigonometric values, $\sin 90^\circ=1$ and $\cos 90^\circ=0$.
So $\cot 90^\circ=\frac{\cos 90^\circ}{\sin 90^\circ}=\frac{0}{1}=0$.
The others are false because $\tan 90^\circ$ and $\sec 90^\circ$ are not defined, and $\csc 0^\circ$ is also not defined.
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