sin^2(20)-sin^2(25)sin(20)+cos^2(50)+cos^2(25)sin20

sin^2(20)-sin^2(25)sin(20)+cos^2(50)+cos^2(25)sin20 求和S=sin^2 1度+sin^2 2度+sin^2 3度+...+sin^2 88度+sin^2 89度 s = 2*sin(x)-sin(2*x)+2/3*sin(3*x)-1/2*sin(4*x)+2/5*sin(5*x)用matlab画图,求教啊 【证明】Sin A+sin B=2Sin 22 sin²20°+sin²25°＋√2sin20°sin25° S(1-sin^2x)d(sinx)为什么=sinx-1/3sin^3x? sin(x^2)/sin^2x 求导 为什么sin-sin^2=1/4 sin(arccos(2sin(a)))= sin²20°+sin80°sin40°且sin(a+b)sin(a-b)=sin^2a-sin^2b 2sin^2 2sin@+cos@等于? 化简sin(-2x) 若sin^2a lim(x(sin)^2) sin(arccos1/2) sin^2(x)求导 sinπ/2是什么意思