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Let a⃗\vec{a} and b⃗\vec{b} be two vectors, such that ∣a⃗∣=3,∣b⃗∣=5|\vec{a}| = 3, |\vec{b}| = 5 and the angle between them is 60°60°, then the value of ∣a⃗+b⃗∣|\vec{a} + \vec{b}| is

Solution

✅ Correct Option: 4

Using ∣a⃗+b⃗∣2=∣a⃗∣2+∣b⃗∣2+2∣a⃗∣∣b⃗∣cos⁡60∘|\vec a+\vec b|^2=|\vec a|^2+|\vec b|^2+2|\vec a||\vec b|\cos 60^\circ, we get 9+25+2(3)(5)(12)=499+25+2(3)(5)\left(\frac{1}{2}\right)=49. Hence the magnitude is 7.

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