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輝念了崔遍匈 >> 厮岑sin(π/3+A)=3/5 夸Cos(5π/6+A) 峙葎? >>

厮岑sin(π/3+A)=3/5 夸Cos(5π/6+A) 峙葎?

‐歌深基宛/ ×(5π/6) -a=(π/3) -a+(π/2) ÷cos(5π/6 -a) =cos[(π/3 -a)+(π/2)] =-sin[(π/3)-a] =-1/3

cosa=-3/5,a((π/2,π), sina=4/5,a((π/2,π), cos(a+π/6)=cosacos(π/6)-sinasin(π/6)=〔3/2*-3/5-1/2*4/5 =(-3〔3-4)/10 sin(a-π/4)=sinacos(π/4)-osasinc(π/4)=(〔2/2)[4/5-(-3/5)]=(7〔2)/10

sin(π/2+a) =sin[π -(π/2+a)] =sin(π/2-a) =cosa =4/5 or -4/5

諒籾音蝪音嬬恬基

sin(A-π)=3/5 sin(π-A)=-3/5 sinA=-3/5 cos2A= 1-2(sinA)^2 = 1- 2(9/25) =7/25

cos5/6*π+a =-cos[π-(5/6*π+a)] =-cos[π/6-a] [sin(a-π/6)]^2=-[cos(a-π/6)]^2-1 -cos└/6-a=-cos(a-π/6) 侭參 -cos5/6π+a+[sin(a-π/6)]^2 =〔3/3-1/3+1 = (2+〔3)/3

喇 cos(α+π/6)=3/5誼sin(α+π/6)=4/5 cos(2a-π/6) =cos(2a+π/3-π/2) =-cos‐π/2-2a+π/3/ =-sin2a+π/3 =-sin2a+π/6 =-2sina+π/6cosa+π/6 =-2x4/5x3/5 =-24/25 仍仍萩寡追

sin(α+π/6)+cosα=4功催3/5 sin(α+π/6)+sin(π/2-α)=4功催3 /5 2sinπ/3cos(a-π/6)=4功催3/5 功催3cos(a-π/6)=4功催3/5 cos(a-π/6)=4/51 cos(2α+2π/3)=-cos(π/3-2α)=1-2cos(a-π/6)峠圭 喇1誼 cos(a-π/6)峠圭=16/25 夸 1-2cos(a-π/6)峠圭=1-...

1 盾: cos(π/2-a) =sina 輝a=π/2扮函誼恷寄峙1

cos(π/6-a)=3/5, sin(π/6-a)=\4/5 sin└/6+a) =sin[π/3-(π/6-a)] =sin(π/3)cos(π/6-a)-cos(π/3)sin(π/6-a) =(〔3/2)*(\4/5)-(1/2)*(3/5) =─4〔3-3/10

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