Law of Cosine|Please Help!

Question

A force with a magnitude of 100 pounds and another with a magnitude of 280 pounds are acting on an object. The two forces have an angle of 80° between them. What is the magnitude of the resultant force?

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Answer 1

Refer to this problem for a detailed explanation of the solution: https://www.wyzant.com/resources/answers/948579/law-of-cosine-please-help

Answer 2

R = (100² + 280² - 2·100·280cos(180° - 80°))^1/2 = 313.248 lb