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我们课本上的一道题:已知sinθ+cosθ=2,求sin2θ的值。现3将sinθ+cosθ=2两边平方,易得sin2θ=-5。39顺水推舟,由2sinθcosθ=-5两边乘以-1后再加1得(sinθ-9cosθ)2=14,9姨姨姨姨姨sinθ+cosθ=2姨sinθ+cosθ=2姨姨姨3解方程组姨3姨姨或姨姨姨姨姨姨姨sinθ-cosθ=姨14姨sinθ-cosθ=-姨14姨9姨9姨姨姨姨姨sinθ=2+姨14姨姨姨sinθ=2-姨14姨姨6姨姨6得姨姨姨或姨姨姨姨姨姨姨姨cosθ=2-姨14姨cosθ=2+姨14姨6姨6不难发现sinθ+cosθ,sinθ-cosθ,sinθcosθ之间有着知其一可求
A question on our textbook: Known sinθ + cosθ = 2, find the value of sin2θ. Now 3 sinθ + cosθ = 2 on both sides of the square, easy to get sin2θ = -5.39 Thrust, by 2sinθcosθ = -5 multiplied by -1 on both sides plus 1 (sinθ-9cosθ) 2 = 14,9 aunt aunt aunt Aunt sin θ + cos θ = 2 aunt aunt aunt 3 solution equation aunt 3 aunt aunt or aunt aunt aunt aunt aunt aunt sinθ-cosθ = aunt 14 aunt sinθ-cosθ = - aunt 14 aunt 9 aunt 9 aunt Aunt aunt Aunt sinθ = 2 + aunt Auntie Aunt sinθ = 2 - Auntie Auntie Auntie Auntie Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aunt Aussie Aunt 6 Aunt 6 is not difficult to find sin θ + cos θ, sin θ-cos θ, sin θ cos θ