圆内接四边形ABCD中,cosA+cosB+cosC+cosD等于( )A.0 �

圆内接四边形ABCD中,cosA+cosB+cosC+cosD等于( )

A.0 B.4 C.2 D.不确定

答案

解析

:∵ABCD是圆内接四边形,

∴∠A+∠C=∠B+∠D=180°.

∴cosA=-cosC,cosB=-cosD.

∴cosA+cosB+cosC+cosD=0.

答案

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圆内接四边形ABCD中,cosA+cosB+cosC+cosD等于( )A.0 �

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