3-2cos^2x=1+2cos^2(90-x)?
回答 (1)
2014-04-19 5:48 am
3 - 2*cos^2(x) = 1 + 2*cos^2(90 - x)
Since sin(x) = cos(90 - x), we have:
3 - 2*cos^2(x) = 1 + 2*sin^2(x)
3 - 1 = 2*sin^2(x) + 2*cos^2(x)
2 = 2(sin^2(x) + cos^2(x))
By Pythagoras, sin^2(x) + cos^2(x) = 1, so we have:
2 = 2*1
2 = 2
Since sin(x) = cos(90 - x), we have:
3 - 2*cos^2(x) = 1 + 2*sin^2(x)
3 - 1 = 2*sin^2(x) + 2*cos^2(x)
2 = 2(sin^2(x) + cos^2(x))
By Pythagoras, sin^2(x) + cos^2(x) = 1, so we have:
2 = 2*1
2 = 2
收錄日期: 2021-04-16 16:29:43
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