求三角函数的值 sin(12000)·cos(12900)+cos(-10200)·sin(-10500)+ta...
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时间：18小时前
sin(1200) cos(1290) + cos(-1020) sin(-1050) + tan(945)
= sin(3 * 360 + 120) cos(3 * 360 + 210) + cos[-(2 * 360 + 300)] sin[-(2 * 360 + 330)]
+ tan(2 * 360 + 225)
= sin(120) cos(210) + cos(300) [-sin(330)] + tan(225)
= sin(180 - 60) cos(180 + 30) - cos(360 - 60) sin(360 - 30) + tan(180 + 45)
= sin(60) [-cos(30)] - cos(60) [-sin(30)] + tan(45)
= √3/2 (-√3/2) - (1/2) (-1/2) + 1
= -3/4 + 1/4 + 1
= -2/4 + 1
= 1/2
