Question

watch the video and then solve the problem given below. click here to watch the video. use the unit circle to find the value of cos(π/2) and even or odd trigonometric functions to find the value of cos(-π/2).

Explanation:

Step1: Recall cosine on unit - circle

On the unit - circle, for an angle $\theta$, the $x$ - coordinate of the point on the unit - circle corresponding to the angle $\theta$ is $\cos\theta$. For $\theta=\frac{\pi}{2}$, the point on the unit - circle is $(0,1)$. So, $\cos\frac{\pi}{2}=0$.

Step2: Use the property of cosine function

The cosine function is an even function, i.e., $\cos(-\theta)=\cos\theta$. Since $\theta = \frac{\pi}{2}$, then $\cos(-\frac{\pi}{2})=\cos\frac{\pi}{2}$.

Answer:

$\cos\frac{\pi}{2}=0$ and $\cos(-\frac{\pi}{2}) = 0$