Question

If |a|= 3, |b|=5, |C| = 7 and a +b+c=0, then the angle between
a and b is​

Answer 1

Answer:

Answer

Correct option is

B

3

π

Given, a+b+c=0

and ∣a∣=5,∣b∣=3,∣c∣=7

⇒a+b=c

On squaring both sides, we get

(a+b)

2

=(−c)

2

⇒∣a+b∣

2

=∣c∣

2

⇒∣a∣

2

+∣b∣

2

+2a⋅b=∣c∣

2

(∵θ be the angle between a and b)

⇒(5)

2

+(3)

2

+2∣a∣∣b∣cosθ=(7)

2

⇒25+9+2⋅5⋅3cosθ=49

⇒30cosθ=15

⇒cosθ=

2

1

=cos60

∘

⇒θ=

3

π

Step-by-step explanation:

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Answer 2

Here is your answer..Hope it helps..