Simply trigo
Algebra
Level
2
x=ycos(120)=zcos(240) then find the value of xy+yz+zx All angles are in degrees.
The answer is 0.
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1 solution
cos(120)=cos (240)=-0.5
so x=-y/2=-z/2
writing whole expression in terms of y we have
answer=-(y^2)/2 +y^2 + -(y^2)/2 =0