(a) Use a calculator to compute the quantity cos 20 cos 40
Chapter 8, Problem 95(choose chapter or problem)
(a) Use a calculator to compute the quantity cos 20 cos 40 cos 60 cos 80. Give your answer to as many decimal places as is shown on your calculator.(b) Now use a product-to-sum formula to provethat the display on your calculator is theexact value of the given expression, not anapproximation.
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