sinθcosθ= 0.25 , θ = ?

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：
呢個係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)

呢個可以幫到你
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sinθcosθ= 0.25
2x(sinθ)(cosθ)=2x0.25
sin(2θ)=0.5
(因為sin30=0.5)
正常計法:
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係一個整數) <---即係話n代咩都岩