问题 解答题
计算下列各式的值.
(1)cos60°-sin2 45°+
3
4
tan2 30°+cos2 30°-sin30°
(2)tan60°-sin60°+tan45°-
1
2(cos30°+tan45°)
答案

(1)cos60°-sin2 45°+

3
4
tan2 30°+cos2 30°-sin30°

=

1
2
-(
2
2
2+
3
4
×(
3
3
2 +(
3
2
2-
1
2

=

1
2
-
1
2
+
1
4
+
3
4
-
1
2

=

1
2

(2)tan60°-sin60°+tan45°-

1
2(cos30°+tan45°)

=

3
-
1
2
+1-
1
2×(
3
2
+1)

=

3
-
1
2
+1-(2-
3

=

3
3
-2
2

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