Sin theta + cos theta = a and (sin theta + cos theta)/ sin theta cos theta = b, then 1. b= 2a/a^2-1 2. a= 2b/b^2-1 3.ab = b^2-1 4.a+b=1?
回答 (1)
2016-08-18 11:33 am
✔ 最佳答案
sinθ + cosθ = a sin²θ + cos²θ + 2sinθcosθ = a²
1 + 2sinθcosθ = a²
sinθcosθ = (a² - 1)/2
(sinθ + cosθ)/(sinθ cosθ) = b
a / ((a² - 1)/2) = b
b = 2a/(a² - 1)
Choose 1.
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