问题 解答题
化简:(1)sin2120°+cos180°+tan45°-cos2(-330°)+sin(-210°)
(2)
sin(θ-5π)cos(-
π
2
-θ)cos(8π-θ)
sin(θ-
2
)sin(-θ-4π)
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°

=(

3
2
)2-(
3
2
)
2
+
1
2

=

1
2

(2)

sin(θ-5π)cos(-
π
2
-θ)cos(8π-θ)
sin(θ-
2
)sin(-θ-4π)

=

(-sinθ)(-sinθ)cosθ
cosθ(-sinθ)

=-sinθ.

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