根号下[sin^2(500°)+sin^2(770°)-cos^2(1620°-x)],(180°

根号下[sin^2(500°)+sin^2(770°)-cos^2(1620°-x)],(180°

(180°

500=360+140
140=180-40
770=720+50
1620=1800-180
(sin500)^2+(sin770)^2-(cos(1620-x))^2
=(sin40)^2+(sin50)^2-(cosx)^2
=1-(cosx)^2
=(sinx)^2
√(sinx)^2=|sinx|=-sinx