若tan=2求sina cosa sina-cosa
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tan(π/4+a)=[tanπ/4+tana)/[1-tanπ/4*tana]=2(1+tana)/(1-tana)=2tana=1/31/(2sinacosa+cos²a)=(sin
tan(a-4/π)=(tana-tanπ/4)/(1+tanatanπ/4)=(tana-1)/(1+tana)=2,所以tana=-3而1/(2sinacosa+cos^2a)=(sin^2a+c
(1+2sinacosa)/(sin平方a-cos平方a)=(sina+cosa)平方/【(sina-cosa)(sina+cosa)】=(sina+cosa)/(sina-cosa)=(tana+1
sina.cosa=1-cos2a
sina+cosa=根号2sina^2+cosa^2+2sinacosa=2sina^2+cosa^2=1sinacosa=0.5
原式=(sin²a+cos²a)/(2sinacosa+cos²a)=(tan²a+1)/(2tana+1)因为tan(π/4+a)=(1+tana)/(1-t
tan(π/4+a)=[tan(π/4)+tana]/[1-tan(π/4)tana]=(1+tana)/(1-tana)=2tana=1/3sinacosa+cos²a=(sinacosa
tan(a+π/4)=2=(tana+tanπ/4)/(1-tanatanπ/4)=(tana+1)/(1-tana)tana=1/3(1+2sinacosa)/(cos^2a-sin^2a)=(si
2,求导f(x)'=2asinx-4cos2x=2asinx-4+8sin^2^x=0,求出x的值,然后对f(x)'再次求导f(x)''>0,(当f(x)'=0.&f(x)''>0时,f(x)为最小值
1.-7/252.tanaAtanB=p(1-q^2)/q(p^2-1)3.3(根号5-1)-5/2
tanA=2运用公式sin2A=2tanA/(1+tan^2A)=4/5sin^2A=tan^2A/(1+tan^2A)=4/5则sinAcosA=sin2A/2=2/5(sinAcosA-sin^2
左边=1+sin^2a/cos^2a=(cos^2a+sin^2a)/cos^2a=1/cos^2a=sina/(sinacos^2a)=sina/(cosa×sinacosa)=tana/(sina
sina^2=36cosa^2sina^2+cosa^2=1→cos^2=1/37式子同除cosa^2再乘cosa^2得(2tana+tana^2)cosa^2=(12+36)1/37=48/37答案
∵tana=tan(π+a)=-4/3,∴2sin²a+sinacosa-3cos²a=(2sin²a+sinacosa-3cos²a)/(sin²a
tan²a-4tana+4=(tana-2)²=0,tana=2,所以sina=2cosa2sin²a+sinacosa+cos²a=8cos²a+2
题目中的sin(a+x)应该是sin(a+π)sin(a+π)=4/5-sina=4/5sina=-4/5∵sinacosa<0∴cosa=3/5[2sin(a-π)+3tan(3π-a)]/4cos
知道tan(a)=-4直接算sina就可以了.tan(a)=sin(a)/cos(a)=-4,所以sin(a)=-4cos(a),sin方(a)+cos方(a)=1.代入得sin方(a)=16/17,
用万能公式,cos2A=sin(π/2+2A)=2tan[(π/4)+A]/{1+tan^2[(π/4)+A]}=4/5sin2A=-cos[(π/2)+2A]=-{1-tan^2[(π/4)+A]}
1-cos2a/sinacosa=1-2(cos2a/2sinacosa)=1-2(cos2a/sin2a)=1-2cot2atana=0.5,tan2a=2tana/(1-tana*tana)=4/