化简sin²(π+α)sin(3π/2+α)tan(π/2-α)/tan(π-α)cos²(-α-π)

化简sin²(π+α)sin(3π/2+α)tan(π/2-α)/tan(π-α)cos²(-α-π)
化简sin²(π+α)sin(3π/2+α)tan(π/2-α)/tan(π-α)cos²(-α-π)

化简sin²(π+α)sin(3π/2+α)tan(π/2-α)/tan(π-α)cos²(-α-π)
sin²(π+α)sin(3π/2+α)tan(π/2-α)/tan(π-α)cos²(-α-π)
=-sin²αcosαcotα/[-tanαcos²α]
=sinαcos²α/[sinαcosα]
=cosα