cotx+2

逄娥哑3775问一道数学题:若cotx - 1=2cotx+1,则(cos2x)/(1+sin2x)等于多少?(sin、cos、cot分别为正弦、余弦、余切) -
薛知该18331215450 ______[答案] cotx-1=2cotx+1, cotx=-2 cosx/sinx=cotx=-2 cosx=-2sinx 因为(cosx)^2+(sinx)^2=1 所以(sinx)^2=1/5 (cosx)^2=4/5 cos2x=(cosx)^2-(sinx)^2=3/5 因为cosx/sinx=-2

逄娥哑3775化简:tanx(cosx - sin)+(sinx+tanx)/(cotx+cscx) -
薛知该18331215450 ______[答案] 中括号提(sinx)平方,前面小括号展开即得结果:sinx

逄娥哑3775 - ∫x cotx d(cotx )该怎么求? -
薛知该18331215450 ______[答案] -∫x cotx d(cotx )=-∫xd(1/2cot x^2)=-1/2xcot x^2-∫cot x^2dx=-1/2xcot x^2+cotx+x+C

逄娥哑3775sin^2xtanx+cos^2x/tanx+2sinxcosx - (1+cosx/sinxcosx)化简 -
薛知该18331215450 ______[答案] sin^2xtanx+cos^2x/tanx+2sinxcosx-(1+cosx/sinxcosx)=sin^3x/cosx+cos^3x/sinx+2sinxcosx-(1+cosx/sinxcosx)=sin^4x.cos^4x/sinxcosx+2sinxcosx-(1+cosx/sinxcosx)=(sin^4x+cos^4x+2sin^2xcos^2x)/sinxcosx-(1+cosx...

逄娥哑3775y=cotx/1+x的导数 -
薛知该18331215450 ______[答案] y'=-cotx/(1+x)^2-1/(1+x)/(Sinx)^2

逄娥哑3775cotx=2,求(sin2x - cos^x)/(2+cos2x)的值 -
薛知该18331215450 ______ cotx=2,求(sin2x-cos^x)/(2+cos2x)的值 cotx=2,tanx=0.5 为简便 令t=tanx 由万能代换公式 sin2x= 2t /(1+t^2)=4/5=0.8 cos2x=(1-t^2)/(1+t^2)=3/5=0.6 cos^x=0.5*(1+cos2x)=0.8 全部代入原式 得(sin2x-cos^x)/(2+cos2x)=(0.8-0.8)/(2+0.6)=0

逄娥哑3775证明(1+cosx)/sinx=cotx/2 -
薛知该18331215450 ______[答案] cos x=2cos(x/2)^2-1; sin x= 2 sin(x/2) cos(x/2); (1+cos x)/(sinx)= (2cos(x/2)^2)/(2 sin(x/2) cos(x/2) )= cos(x/2)/sin(x/2)=1/cot(x/2)

逄娥哑3775tanx+cotx的周期 -
薛知该18331215450 ______ 可以用图象法,正弦和余弦函数都是以为π周期,但二者叠加后就变为π/2 π/2

逄娥哑3775(cos2x)的1+cotx²次方的极限,当x趋向于0时. -
薛知该18331215450 ______[答案] lim(x→0) (cos2x)^(1+(cotx)^2) =lim(x→0) (cos2x)^(1/(sinx)^2) =lim(x→0) (1-2(sinx)^2)^(1/(sinx)^2) =lim(x→0) (1-2(sinx)^2^(1/[-2(sinx)^2])^(-2) =e^(-2)

逄娥哑3775微分(tanx+cotx)平方 -
薛知该18331215450 ______[答案] y= (tanx +cotx)^2 dy = 2(tanx +cotx)d(tanx +cotx) = 2(tanx +cotx)[(secx)^2-(cscx)^2]dx