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Answered by
7
Answer:
60°
Step-by-step explanation:
Given, |a| = 3, |b| = 5, |c| = 7.
Given, a + b + c = 0
⇒ |a + b| = |-c|.
On squaring both sides, we get
⇒ |a + b|² = |-c|²
⇒ |a|² + |b|² + 2|a||b|cosθ = |c|²
⇒ 9 + 25 + 2 * 3 * 5 * cosθ = 49
⇒ 34 + 30 cosθ = 49
⇒ 30 cos θ = 15
⇒ cos θ = 15/30
⇒ cos θ = 1/2
⇒ cos θ = cos 60°
⇒ θ = 60°.
Therefore, the angle between a and b = 60°.
Hope it helps!
Answered by
0
Answer:
60°
Step-by-step explanation:
|a| = 3, |b| = 5, |c| = 7.
a + b + c = 0
|a + b| = |-c|.
On squaring both sides, we get
|a + b|² = |-c|²
|a|² + |b|² + 2|a||b|cosθ = |c|²
9 + 25 + 2 * 3 * 5 * cosθ = 49
34 + 30 cosθ = 49
30 cos θ = 15
cos θ = 15/30
cos θ = 1/2
cos θ = cos 60°
θ = 60°.
the angle between a and b = 60°.
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