求证：arctan 1/2+arctan 1/5+arctan 1/8=π/4

求证：arctan 1/2+arctan 1/5+arctan 1/8=π/4 cos[arctan(1/2) - arctan(-2)]=? arctan arctan(-2)+arctan(-3)=? arctan(1/3)+arctan(1/2)的值为? 级数求和：arctan(1/2)+arctan(1/2^2)+arctan(1/2^3)+...+arctan(1/2^n)+... arctan(1/2)?是多少?谢谢 不定积分arctan(1+x^1/2)dx arctan(((2X)/(1-X))^2)导数 cos[2arctan(-1/2)]=? 求值：sin[1/2arctan(-4/3)] 求微积分arctan(x^1/2)dx arctan根号（x^2-1)求导, arctan（x）^1/2的不定积分 计算cos(1/2arctan(-3/4)) y=arctan（x^2+1） arctan-1等于多少 arctan(1/x)求导