Deepak Scored 45->99%ile with Bounce Back Crack Course. You can do it too!

# Solve this following

Question:

Let $\hat{a}$ and $\hat{b}$ be two unit vectors. If the vectors $\vec{c}=\hat{a}+2 \hat{b}$ and $\vec{d}=5 \hat{a}-4 \hat{b}$ are perpendicular to each other, then the angle between $\hat{a}$ and $\hat{b}$ is :

1. $\frac{\pi}{4}$

2. $\frac{\pi}{6}$

3. $\frac{\pi}{2}$

4. $\frac{\pi}{3}$

Correct Option: , 4

Solution: