Question

What is the dot product of two vectors of magnitude 3 and 5, if angle between them is ${60}^{\circ }?$

• A. $5.2$
• B. $7.5$
• C. $8.4$
• D. $8.6$

Answer 1

The correct option is B $7.5$

Given: a=3, b=5 ,$\theta$ =${60}^o$
Dot product, a⃗.b⃗=ab.cosθ\vec{a}.\vec{b}=ab.cos\thetaa.b=ab.cosθ
Thus, dot product = 3×5×cos600=7.53\times 5\times cos{60}^{0}=7.53×5×cos600=$3\times 5\times \frac{1}{2}$ = 7.5