Question

The angle between the two vectors$\overrightarrow{A} = 3\widehat{i} + 4\widehat{j} + 5\widehat{k}$and $\overrightarrow{B} = 3\widehat{i} + 4\widehat{j} + 5\widehat{k}$ is

• A. 60°
• B. Zero
• C. 90°
• D. None of these

Answer 1

Answer: (D)

None of these

Answer 2

$\cos\theta = \frac{\overset{\rightarrow}{A}.\overset{\rightarrow}{B}}{|A||B|} = \frac{9 + 16 + 25}{\sqrt{9 + 16 + 25}\sqrt{9 + 16 + 25}}$=$\frac{50}{50} = 1$

⇒$\cos\theta = 1$ $\therefore$ $\theta = \cos^{- 1}(1)$