cos 2x等于多少
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(1)根据图信息可知sina=4/5cosa=3/5∴(sina^2+sin2a)/(cosa^2+cos2a)=(sina^2+2sinacosa)/(cosa^2+cosa^2-sina^2)=(
cos2X=(cosX)^2-(sinX)^2=2*(cosX)^2-1
再答:一定等于
f(sinx)=cos2x=1-2sin²x∴f(t)=1-2t²∴f(cosx)=1-2cos²x=-cos2x
sin^2x+cos^2x=1sin^2x+9sin^2x=1sin^2x=1/10Cos2X+Sin2X=cos^2x-sin^2x+2sinxcosx=9sin^2x-sin^2x+6sin^2x
1/2*sin2x再问:过程?
(sinx/cosx+cosx/sinx)cos^2x-sin^2x=sinx*cosx+cos^3x/sinx-sin^3x/cosx-cosx*sin=(cos^4x-sin^4x)/(sinx*
f(sinx(π/2-x))=cos(π-2x)f(cosx)=-cos(2x)
题目条件不充分啊cos2x+sin2x=1cos2x=cos^2x-sin^2xsin2x=2sinxcosxcos2x+sin2x=cos^2x-sin^2x+2sinxcosx
(积分符号Pi到0)√(1-cos2x)dx=-2√2limx趋向0+,lnx=-∞e-2√2原式=+∞
sinx/cosx=tanx所以sin2x/cos2x=tan2x
sin2x+cos2x=√2(√2/2sin2x+√2/2*cos2x)=√2(cospai/4sin2x+sinpai/4cos2x)=√2sin(2x+pai&#4
f(sinx)=1-cos2x=2(sinx)^2,既有f(x)=2x^2,故f(cosx)=2*(cosx)^2=1+cos2x.
lim1/cosx=1(x->0)当x->0时,cosx和cos2x都趋于1,但是在取极限的式子中二者一般不能随便换.比如lim(1-cosx)/(1-cos2x)=1/4(x->0)不是1你要是问l
1/2sin4x
sin15度=cos75度因为f(cosx)=cos2x所以f(sin15度)=f(cos75度)=cos(2*75度)=cos150度=-cos30度=-根号3/2
原式=∫4cos2x/sin²2xdx=2∫cos2x/sin²2xd(2x)=2∫dsin2x/sin²2x=-2/sin2x+C再问:能把cos2x化成cos&sup
lim(x→0)(1-cos2x)/sinx=lim(x→0)2sin²x/sinx=lim(x→0)2sinx=0
limx0时1-cos2x/sinx=limx0时[(2x)²/2]/x=0