The simultaneous equations in x,y

xcosθ - ysinθ = 2

xsinθ + ycosθ = 1

are solvable for how many values of θ in the range 0<= θ < 2pi

I was told that it is for all values, using the idea of discriminants. But I haven't learnt this yet, so I am meant to use some other method. Any advice?

Thanks