sinθcosθ= 0.25 , θ = ?

更新1:

超凡學生 : 180+(-1)n(30)
where n is an integer. 咩黎?

sinθcosθ= 0.25 1/2sin2θ=0.25 sin2θ=0.5 2θ=180+(-1)n(30)
where n is an integer. θ=90o+(-1)n(15o) 2009-06-09 17:25:59 補充： 呢個系GENERAL SOLUTION 2009-06-09 17:30:18 補充： 2θ=180n度+(-1)^n(30度)
where n is an integer. θ=90n度+(-1)^n(15度)
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sinθcosθ= 0.25 2x(sinθ)(cosθ)=2x0.25 sin(2θ)=0.5 (因為sin30=0.5) 正沖源雀常計法: sin(2θ)=0.5 2θ=30 θ=15 general formal: sin(2θ)=0.5 2θ=180+(-1)n(30) θ=90+(-1)n(15)
where n is an integer(n系一散早個整數(shù)) <---即裂讓系話n代咩都巖
參考: ME