A missile is launched to hit a specified target located at the origin in the x-y coordinate plane. It is assumed that x and Y are independent and normally distributed such that
their joint density is given by:
fxY(x,y)=1/2πσ² e-(x²+y²)²σ²

a) determine the corresponding density function in polar coordinates r and θ, i.e. find
fᵣ₀(r,θ) where x=rcosθ and y=rsinθ