计算或化简:
(1)
(2)
(3)
(4)sin230°+cos245°+sin60°?tan45°.
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解:
(1),
=(2+)(-2),
=(2+2)(2-2),
=(2)2-(2)2,
=12-20,
=-8;
(2),
=3-×-×m,
=3--,
=(3--),
=;
(3),
=(3×-2×+4)÷2,
=÷2,
=;
(4)sin230°+cos245°+sin60°?tan45°,
=()2+()2+×1,
=++,
=+,
=.
解析分析:(1)化简二次根式后,再运用平方差公式求出比较简单;
(2)把二次根式化为最简二次根式,再进行合并同类二次根式即可得出