Question

At $\theta ={90}^{\circ }$, which of the following angles are not defined?

• A. $cot\theta ,sin\theta$
• B. $tan\theta ,cosec\theta$
• C. $cot\theta ,tan\theta$
• D. $tan\theta ,sec\theta$

Answer 1

The correct option is D $tan\theta ,sec\theta$

We know that, $tan\theta =\frac{sin\theta }{cos\theta }$.
At $\theta ={90}^{\circ },cos{90}^{\circ }=0$.
So, tan $\theta$ is not defined at $\theta ={90}^{\circ }$.

Similarly, $sec\theta =\frac{1}{cos\theta }$.
At $\theta ={90}^{\circ },cos{90}^{\circ }=0$.
So, $sec\theta$ is not defined at $\theta ={90}^{\circ }$.