问题
解答题
化简:(1)sin2120°+cos180°+tan45°-cos2(-330°)+sin(-210°) (2)
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答案
(1)sin2120°+cos180°+tan45°-cos2(-330°)+sin(-210°)
=sin2(180°-60°)-1+1°-cos2(360°-30°)-sin(180°+30°)
=sin260°-1+1-cos230°+sin30°
=(
)2-(3 2
)2+3 2 1 2
=
.1 2
(2)sin(θ-5π)cos(-
-θ)cos(8π-θ)π 2 sin(θ-
)sin(-θ-4π)3π 2
=(-sinθ)(-sinθ)cosθ cosθ(-sinθ)
=-sinθ.