Principle of Mathematical Induction

Principle of Mathematical Induction

Question

In triangle ABC, if a = 18, b = 24, c = 30, find cosB


Answer

Applying cosine formula, we have
                   space space space cosB space equals space fraction numerator straight c squared plus straight a squared minus straight b squared over denominator 2 ca end fraction space equals space fraction numerator 900 plus 324 minus 576 over denominator 2 cross times 30 cross times 18 end fraction space equals space fraction numerator 648 over denominator 2 cross times 30 cross times 18 end fraction space equals space 3 over 5

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