The equation sin2θ=x2+y22xy, x, y≠0 is possible if
x=y
x=−y
2x=y
4x=y
Given, sin2θ=x2+y22xy
∴x, y must have same sign
Also, 0≤x2+y2≤2xy
⇒0≤x2+y2−2xy≤0
⇒0≤(x−y)2≤0
⇒x=y
The equation of the parabola whose focus is the point (0, 0) and the tangent at the vertex is x-y+1=0 is