Question

R=
5² + 6² + 2(5)(6) cos 60
find value of R​

Answer 1

Answer:

25+36+60×1/2

25+36+30

91

Answer 2

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$\to$ 91

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$\to {(5)}^{2} + {(6)}^{2} + 2(5)(6) \cos(60) \\ \\ \to 25 + 36 + 60 \times \frac{1}{2} \\ \\ \to 61 + \frac{60}{2} \\ \\ \to 61 + 30 \\ \\ \to 91$