f(x)=(sin2x-cos2x+1)/(2sinx)
=(2sinxcosx+2sin^2 x)/(2sinx)
=cosx+sinx (sinx≠0)
1.
f(x)定义域{x|x≠πk,k∈Z}
2.
α是锐角,且tanα=4/3
α=arc tang(4/3)
用计算器可得具体值,是个无理数