sint/(1-cost)=cost/2怎么推?

sint/(1-cost)=cost/2怎么推? sint/1-cost=什么 sint/(1-cost)求导 (cost-sint)/(sint-cost) 的结果不知道等不等于 -(sint-cost)/(sint-cost)也就是-1 为什么sint/(1-cost)=cot(t/2) 为什么∫(2sint+cost)+2(2cost-sint)/2sint+cost dt = (t+2ln|2sint+cost|)+C? t趋于0时为什么lim(sint+cost-1)/t=lim(cost-sint)=1) ∫dt/(1+sint+cost) (sint cost)^2 的不定积分 求x=e^t*cost,y=e^t*sint所确定的函数的二阶导数,求讲解x't=(e^t)(sint+cost)y't=(e^t)(cost-sint)x''t=(e^t)(sint+cost+cost-sint)=2(e^t)costy''t=(e^t)(cost-sint-sint+cost)=-(e^t)sintdy/dx=(cost-sint)/(sint+cost)d^2 y/d(x^2)=d(dy/dx)/dx=(y''x ∫cost/(sint+cost)dt 此参数方程为什么这么解x=2(t-cost)y=2(1-sint)求dy/dx.答案是dy/dx = -cost/(1+sint)为什么dx= 2(1+sint)dt为什么dy= -2cost 证明：f(x)=x*cos(x)不是周期函数证明：假设y=xcosx是周期函数,因为周期函数有f(x+T)=f(x)xcosx=（x+T)cos(x+T)=xcosx*cosT-xsinx*sinT+Tcosx*cosT-Tsinx*sinT所以cosT=1 T=kπ/2-xsinx*sinT+Tcosx*cosT-Tsinx*sinT=0-xsinx*sinT-Tsinx*si 1/(sint)^2和1/(cost)^2的不定积分 怎么求s=(1+sint)/(1+cost)的导数? ∫sint^2 cost^2 dt=?怎么算啊 t趋于0时lim(sint+cost-1)/t=lim(cost-sint)=1)t趋于0时为什么lim(sint+cost-1)/t=lim(cost-sint)=1) tant/2是怎么转化为sint/1+cost的