SIN 90 = SIN 30 =（-1）=45-99.9=25X（-0.4）=125X-8=1/2+3/1-=5除以（-0.1）=5- （-5） =

计算:sin方10°+sin方20°+sin方30°+sin方40°+sin方50°+sin方60°+sin方70°+sin方80°+sin方90°= sin²1°+sin²2°+sin²3°+...+sin²88°+sin²89°+sin²90°=等于多少? sin^20+cos^50=sin^30sin^70= sin(45+&)sin(45-&)=1/6,90>& 为什么sin-sin^2=1/4 sin²1°+sin²2°+.+sin²89°+sin²90°=? 求值:sin²1°+sin²2°+...+sin²89°+sin²90°= sin²1°+sin²2°+……+sin²90°= sin是什么符号?sin的值是多少?sin 30=1/2为什么? sin²10°+sin²20°+sin²30°+……+sin²80°+sin²90°=? 求证:sin^2/(sin-cos) - (sin+cos)/(tan^2 -1) =sin+cos sin²0+sin²1+sin²2+……+sin²180= sin阿尔法+sin贝塔=? sin(sinx)/x,x 趋于0的极限sin(sin(x))/x=[sin(sin(x))/sin(x)]*sin(x)/x=1*1=1sin(sin(x))/sin(x)这一部我不明白阿 傅里叶级数作图f（x）=2sin[x] - sin[2x] + 2/3sin[3x] - 1/2sin[4x]我用mathematica输入程序Plot[{2sin[x],-2sin[x],2sin[x] - sin[2x],-2sin[x] + sin[2x],2sin[x] - sin[2x] + 2/3sin[3x],-2sin[x] + sin[2x] - 2/3sin[3x],2sin[x] - sin[2x] + 2/3si 已知:sin^2 30度+sin^2 90度+sin^2 150度=3/2,sin^2 5度+sin^2 65度+sin^2 125度=3/2,观察规律,请你写出一般性的命题. 已知sin^2(30°)+sin^2(90°)+sin^2(150°)=1.5sin^2(5°)+sin^2(65°)+sin^2(125°)=1.5 观察两等式 写出一般性命题 并给出证明 在Rt△ABC中,角C=90°,求证sin^2A+sin^2B=1,并利用上式求sin^21°+sin^22°+sin^32°+……+sin^289°的值