Question

find the value of a and b if Angle 5+ angle 3 / angle 5. - angle 3 = a + b angle 15​

Answer 1

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12th

Maths

Vector Algebra

Scalar or Dot Product

If a + b + c = 0 and |a| = ...

MATHS

If a+b+c=0 and ∣a∣=5,∣b∣=3 and ∣c∣=7 then angle between a and b is

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VIDEO EXPLANATION

ANSWER

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

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