Question

If x cosB - COSA = 0 and y sinB - COSA = 0, then
the value of cos2A will be
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Answer 1

Answer:

ANSWER

Given cosA+cosB+cosC=0-----equ(1)

We know x3+y3+z3−3xyz=(x+y+z)(x2+y2+z2−xy−xz−yz).

 

Let x=cosA,y=cosB and z=cosC 

cosA+cosB+cosC=x+y+z=0 , so this identity becomes 

x3+y3+z3−3xyz=0

x3+y3+z3=3xyz 

cos3(A)+cos3(B)+cos3(C)=3cosAcosBcosC

Now, cos(3A)=cos(2A+A)

=cos(2A)cosA−sin(2A)sinA 

= (cos2(A)−sin2(A))cosA−(2sinAcosA)sinA

= cos3(A)−3cosAsin2(A)

=cos3(

Step-by-step explanation:

I think this is the answrr