计算:cos 60°-3tan30°+tan60°+2sin245°.
计算:
计算:sin30°+cos60°-tan45°-tan30°·tan60°
计算:tan60°·cos30°-3tan30°·tan45°
计算5sin30°+2cos245°-tan260°的值是( )
A. B. C.- D.1
在△ABC中,若,则∠C的度数为( )
A.30° B.60° C.90° D.120°