问题
填空题
求值:①2log39+log2
②sin2120°+cos180°+tan45°-cos2-(-330°)+sin(-210°)=______. |
答案
①2log39+log2
-0.70-2-1+251 4 1 2
=4log33-2log22-1-
+5=4-2-1-1 2
+51 2
=51 2
②sin2120°+cos180°+tan45°-cos2-(-330°)+sin(-210°)
=(
)2-1+1-cos230°-sin210°3 2
=
-(3 4
)2+sin30°=sin30°3 2
=1 2