tana=-1/2则sin2a+2cos2a/4cos2a-4sin2a的值是?

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tana=-1/2则sin2a+2cos2a/4cos2a-4sin2a的值是?tana=-1/2则sin2a+2cos2a/4cos2a-4sin2a的值是?tana=-1/2则sin2a+2cos

tana=-1/2则sin2a+2cos2a/4cos2a-4sin2a的值是?
tana=-1/2则sin2a+2cos2a/4cos2a-4sin2a的值是?

tana=-1/2则sin2a+2cos2a/4cos2a-4sin2a的值是?
tana=-1/2
故tan2a=2tana/[1-(tana)^2]=2×(-1/2)/[1-(-1/2)^2]=-4/3

(sin2a+2cos2a)/(4cos2a-4sin2a) 分子分母同除以cos2a
=(tan2a+2)/(4-4tan2a)
=(-4/3+2)/[4-4×(-4/3)]
=1/14