find the value of cos²45-sin²15
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Answer:
cos²45 - sin²15
= cos²45 - (1/2)(1 - cos(2 * 15))
= cos²45 - (1/2)(1 - cos 30)
= (√2/2)² - (1/2)(1 - √3/2)
= 1/2 - (1/2 - √3/4)
= √3/4.