[Toán 11]giai giup minh bai luong giac nay voi

C

connguoivietnam

căn(sinx)+sinx+cosx+căn(cosx)=1
căn(sinx)+căn(cosx)=(1-(sinx+cosx))
sinx+cosx+2căn(sinxcosx)=1-2(sinx+cosx)+(sinx+cosx)^2
đặt sinx+cosx=t đk 0<=t<=căn2
sinxcosx=(t^2 -1)/2
t+2căn((t^2 -1)/2)=1-2t+t^2
2căn((t^2 -1)/2)=1-3t+t^2
2(t^2 -1)=(1-3t+t^2)^2
2t^2 -2=(1-3t)^2+2t^2(1-3t)+t^4
2t^2 -2=1-6t+9t^2+2t^2-6t^3+t^4
t^4-6t^3+9t^2-6t+3=0
 
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P

phaihocthatgioi

can(sinx)+sinx+sosx+can(sosx)=1
can(sinx)+can(sosx)+sinx+sosx=1
ta binh phuong 2 ve
sinx+sosx+sin^2x+sos^2x=1
(sinx+sosx)+(sin^2x+sos^2x)=1
theo cong thuc thi (sin^2x+sos^2x)=1 nen
(sinx+sosx)+1=1
sinx+sosx=0
chia ca hai ve cho sosx ta duoc
tanx=-1
ta co x=kpi
 
B

bikent12

cos5x*cos3x+sin7x*sinx=cos2x*cos4x
sin5x-2sinx(cos2x+cos4x0=sinx
sinx*sin(pi/3-x)*sin(pi/3+x)=1/4*sin3x
sin(2x+pi/3)*cos(x-pi/6)-cos(2x+pi/3)*cos(2pi/3-x)=cosx
 
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