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Sides of 5, 7 and 8 form a triangle. What is the angle opposite the side of length 7?
A30°
B45°
C60°
D90°
Answer & Solution
Correct answer: C. 60°
cos θ = (25 + 64 − 49)/(2·5·8) = 1/2, so θ = 60°.
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