问题
解答题
计算下列各式的值. (1)cos60°-sin2 45°+
(2)tan60°-sin60°+tan45°-
|
答案
(1)cos60°-sin2 45°+
tan2 30°+cos2 30°-sin30°3 4
=
-(1 2
)2+2 2
×(3 4
)2 +(3 3
)2-3 2 1 2
=
-1 2
+1 2
+1 4
-3 4 1 2
=
;1 2
(2)tan60°-sin60°+tan45°-1 2(cos30°+tan45°)
=
-3
+1-1 2 1 2×(
+1)3 2
=
-3
+1-(2-1 2
)3
=
.3
-23 2