Question
Asked Apr 7, 2019
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Did exact value using half-angle identities 

a) sin 22.5°

b) cos75°

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Expert Answer

Step 1

to evaluate the (exact , using radicals, etc) values of the given trigonometric ratios using standard half-angle identities

Step 2

In  this exercise, the exact expressions for sin 22.5 and cos 75 are to be found. (no tables , calculators). These values are obtained by using the trigonometric ratios of the corresponding double angles , namey 45 and 150 degrees

Step 3
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Trigonometry

Trigonometric Ratios

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