Find the exact value of the trigonometric expression given cos (22.5 ).

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asked Nov 8, 2019 220k views

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Find the exact value of the trigonometric expression given cos (22.5 ).

Mathematics
high-school

Syed Abidur Rahman asked

by Syed Abidur Rahman

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use the identity cos^2 (a/2) = 1/2 (1 + cos a) so

cos^ 2 22.5 = cos^2 (45/2) = 1/2 ( 1 + cos 45) = 1/2(1 + sqrt2/ 2)4 = 1/2 + sqrt2/4

cos 22.5 = sqrt ( 1/2 + sqrt2/4) Answer

Jorick Spitzen answered Nov 11, 2019

by Jorick Spitzen

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