为什么1/(cost(cost-1))可以变成1/cost-1/(cost-1),

为什么1/(cost(cost-1))可以变成1/cost-1/(cost-1), 1/cost的不定积分 ∫dt/(1+cost) 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 t趋于0时为什么lim(sint+cost-1)/t=lim(cost-sint)=1) sint/(1-cost)=cost/2怎么推? ∫dt/(1+sint+cost) sint/1-cost=什么 t/(1+cost)的不定积分 为什么sint/(1-cost)=cot(t/2) 因为t趋于0时,lim(sint cost-1)/t=lim(cost-sint)=1这是为什么 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) 1/(1 cost)的不定积分怎么求 (1/(1+sint+cost))dt不定积分 求积分 ∫ [ 1 / (cost)^3 ]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 do does ； cost costs的用法!1：how much do the carrots cost?the carrots cost three dollars.2：how much does the tea cost?the tea costs two euros.3：how much does a movie ticket cost?a movie ticket costs nine pounds.问：为什么第一句用d