问题 填空题
求值:①2log39+log2
1
4
-0.70-2-1+25
1
2
=______;
②sin2120°+cos180°+tan45°-cos2-(-330°)+sin(-210°)=______.
答案

①2log39+log2

1
4
-0.70-2-1+25
1
2

=4log33-2log22-1-

1
2
+5=4-2-1-
1
2
+5

=5

1
2

②sin2120°+cos180°+tan45°-cos2-(-330°)+sin(-210°)

=(

3
2
2-1+1-cos230°-sin210°

=

3
4
-(
3
2
2+sin30°=sin30°

=

1
2

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