Let P(3,2,3),Q(4,6,2) and R(7,3,2) be the vertices of .

Question

Let $P(3,2,3),Q(4,6,2)$ and $R(7,3,2)$ be the vertices of $	rianglePQR$. Then, the angle $\angleQPR$ is

Accepted Answer

Direction ratio of $$\mathrm{PR}=(4,1,-1)$$

Direction ratio of $$\mathrm{PQ}=(1,4,-1)$$

Now, $$\cos \theta=\left|\frac{4+4+1}{\sqrt{18} \cdot \sqrt{18}}\right|$$

$$\theta=\frac{\pi}{3}$$

Solutions · 1