cosA cosC= 2cos[(A C) 2]cos[(A-C) 2]
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∫(1+cos^2x)/cos^2xdx=∫1/cos^2x+1dx=∫1/cos^2xdx+x=∫1d(tanx)+x=tanx+x+c
∵p=√(x^2+y^2)p*cosa=xp*sina=y∴由p=cosa/cos2a两边取倒数,得1/p=cos2a/cosa=[(cosa)^2-(sina)^2]/cosa=cosa-(sina
(cosx)^2-(sinx)^2=cos2x,变换加移项能的到你写的公式
比如帕尔/6
COS(X+Y)COS(X-Y)=(COSX*COSY-SINX*SINY)(COSX*COSY+SINX*SINY)=(COSX*COSY)^2-(SINX*SINY)^2=COS^2X(1-SIN
先可以把cos^290度和cos^2180度算出来=1首项cos^21度和末项cos^2179相加=2cos^21度以此类推,原始变成:2(cos^21度+cos^22度+...+cos^289度)+
解应为(sinα+cosα)/(sinα-cosα)=2两边平方得(sin²α+cos²α+2sinαcosα)/(sin²α+cos²α-2sinαcosα)
1/2+2cosAcosC=cos(A-C)1/2+2cosAcosC=cosAcosC+sinAsinCcosAcosC-sinAsinC=-1/2∴cos(A+C)=-1/2∵A+C∈(0,π)∴
∵a+c=2b∴sinA+sinc=2sinB即sinA+sinC=2sin(A+C)由和差化积、二倍角公式得:2sin[(A+C)/2]×cos[(A-C)/2]=4sin[(A+C)/2]×cos
89°和1°互余,∴cos89°=sin1°∴cos²1°+cos²89°=cos²1°+sin²1°=1同理cos²2°+cos²88°=
sin^2/(sin-cos)-(sin+cos)/(tan^2-1)=sin^2/(sin-cos)-(sin+cos)/[(sin^2/cos^2)-1]=sin^2/(sin-cos)-(sin
Pi表示派.cos(2pi/7)+cos(4pi/7)+cos(6pi/7)=1/[2sin(2pi/7)]*[2sin(2pi/7)cos(2pi/7)+2sin(2pi/7)cos(4pi/7)+
=[1-(sin²a+cos²)(sin^4a-sin²acos²a+cos^4a)]/cos²a(1-cos²a)=[1-(sin^4a+
原题是这样子吧:cos(a+b)cos(a-b)=1/5,则(cosa)^2-(sinb)^2=?cos(a+b)cos(a-b)=(cosacosb-sinasinb)(cosacosb+sinas
你的式子有一项好像抄错了如果原题是求证a²(cos2B-cos2C)+b²(cos2C-cos2A)+c²(cos2A-cos2B)=0的话证明如下:a²(co
(1)∵cosAcosC=3a2b−3c,∴cosAcosC=3sinA2sinB−3sinC∴2cosAsinB−3cosAsinC=3sinAcosC∴2cosAsinB=3sin(A+C)∴co
解题思路:利用三角函数公式求解解题过程:varSWOC={};SWOC.tip=false;try{SWOCX2.OpenFile("http://dayi.prcedu.com/include/re
=sin4Asin2A+cos4Acos2A-cos2A(cos4Acos2A-sin4Asin2A)=cos2A+cos2Acos6A=cos2A(1+cos6A)
cos(-2/3)π=-0.5