sintcost分之cost

空莘婕3986怎么求s=(1+sint)/(1+cost)的导数? -
席狐纨18016059308 ______[答案] ds/dt=[cost(1+cost)-(1+sint)(-sint)]/(1+cost)² =(cost+cos²t+sint+sin²t)/(1+cost)² =(cost+sint+1)/(1+cost)²

空莘婕3986sin2分之x - cos2分之x=3分之1,则sinx= -
席狐纨18016059308 ______[答案] 答: 设x/2=t则: sinx=sin2t=2sintcost (sint-cost)²=1/9 sin²t-2sintcost+cos²t=1/9 1-2sintcost=1/9 2sintcost=8/9 所以2sintcost=sin2t=sinx=8/9

空莘婕3986arccos(x)=arctan(x)求解x的值. -
席狐纨18016059308 ______[答案] 令arccosx=arctanx=t, 则有cost=tant=x,即sint/cost=sint/x=x, 可得sint=x^2. 根据(sint)^2+(cost)^2=1得 x^2+x-1=0, 解得x=(-1+根号5)/2 或 x=(-1-根号5)/2.

空莘婕3986(2sintcost)dt等于多少?答案说是sint2t,中间过程是怎么算的? -
席狐纨18016059308 ______[答案] (2sintcost)dt =2sint (cost dt) =2sint dsint = d(sin²t)

空莘婕3986x=sint+cost y=sintcost 化为普通方程. -
席狐纨18016059308 ______[答案] ∵(sint+cost)²=sin²t+2sintcost+cos²t=1+2sintcost ∴x²=1+2y ∴y=x²/2-1/2

空莘婕3986已知sint+cost=1,设s=cost+isint,求f(s)=1+s+s 2 +…s n -
席狐纨18016059308 ______ sint+cost=1 ∴(sint+cost) 2 =1+2sint?cost=1 ∴2sint?cost=sin2t=0 则cost=0,sint=1或cost=1,sint=0,当cost=0,sint=1时,s=cost+isint=i 则f(s)=1+s+s 2 +…s n = 1+i,n=4k+1 i,n=4k+2 0,n=4k+3 1,n=4(k+1) (k ∈N + ) 当cost=1,sint=0时,s=cost+isint=1 则f(s)=1+s+s 2 +…s n =n+1

空莘婕39861/tant+1 的不定积分怎么求? -
席狐纨18016059308 ______[答案] 令A=∫1/(tant+1)dt =∫cost/(sint+cost)dt B=∫sint/(sint+cost)dt 则A+B=∫cost/(sint+cost)dt+∫sint/(sint+cost)dt =∫(cost+sint)/(sint... =∫1/(cott+1)dt =1/2*(t-ln|sint+cost|)+C 如果是∫[(1/tant)+1]dt =∫(cott+1)dt =∫cost/sintdt+t =∫d(sint)/sint+t =ln|sint|+t+C

空莘婕3986最后cosA等于1吗 -
席狐纨18016059308 ______ 不,等于二分之一,选B

空莘婕3986i=cost - sint 求一个周期的图像 提示:原式=根号2【( - 2分之根号2)sint+2分之根号2cost】 -
席狐纨18016059308 ______[答案] 这道题不需要化开、、 括号里面用正弦定理 可以化为cos5/4π*sint+sin5/4π*cost=sin(5/4π+t) 所以i=根号2sin(5/4π+t) 就可以画出图像了.

空莘婕3986t属于(0,π),sint+cost=1/3,求cos2t -
席狐纨18016059308 ______[答案] ∵(sint+cost)^2 =1+2sintcost =1/9 ∴sintcost=-4/9 ∵t∈(0,π) ∴sint>0 ∵sintcost