tanx=2 x∈(π,3π/2),求[sin(π-α)+2sin(3π/2+α)]/[cos(3π-α)+1]的值.

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tanx=2 x∈(π,3π/2),求[sin(π-α)+2sin(3π/2+α)]/[cos(3π-α)+1]的值.
tanx=2 x∈(π,3π/2),求[sin(π-α)+2sin(3π/2+α)]/[cos(3π-α)+1]的值.

tanx=2 x∈(π,3π/2),求[sin(π-α)+2sin(3π/2+α)]/[cos(3π-α)+1]的值.
[sin(π-α)+2sin(3π/2+α)]/[cos(3π-α)+1]
=[sinα-2cosα]/[-cosα+1]
=[sinα/cosα-2cosα/cosα]/[-cosα/cosα+1/cosα]
=[tanα-2]/[-1+1/cosα]
=[2-2]/[-1+1/cosα]
=0/[-1+1/cosα]
=0