Simplify completely: cos 75˚ cos 10˚ - sin 75˚ sin 10˚?
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1 Answer
May 17, 2018
cos 90
Explanation:
Use trig identity:
cos (a + b) = cos a.cos b - sin a.sin b
In this case:
cos 75.cos 15 - sin 75.sin 15 = cos (75 + 15) = cos 90
