cos585°/tan495°+sin690°的值是多少?

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cos585°/tan495°+sin690°的值是多少?cos585°/tan495°+sin690°的值是多少?cos585°/tan495°+sin690°的值是多少?cos585°=cos(5

cos585°/tan495°+sin690°的值是多少?
cos585°/tan495°+sin690°的值是多少?

cos585°/tan495°+sin690°的值是多少?
cos585°
=cos(585°-360°)
=cos225°
= -cos45°= -√2 /2
tan495°
=tan(135°+360°)
=tan135°= -1

sin690°
=sin(720°-30°)
=sin(-30°)
= -0.5
所以
cos585°/tan495°+sin690°
=(-√2 /2) / (-1) -0.5
=√2 /2 -0.5
=(√2 -1)/2
=0.207