that its distance from P is always increasing from its launch until its fall back to the ground. Find

**ALL**the possible values of θ with which the projectile could have

been thrown. You can ignore air resistance.

My attempt.

y=Vosinθ*t -0.5gt^2

x=Vocosθ*t

√(x^2 + y^2) = √((Vocosθ*t)^2+(Vosinθ*t-0.5gt^2)^2)

We have to take the derivative of the magnitude to time

dD/dt √((Vocosθ*t)^2+(Vosinθ*t-0.5gt^2)^2)

I want dD/dt > 0 so it is always positive

after derivation i get

t(g^2 * t^2 -3Vo*g*sin(θ)t +2Vo^2)>0

Let the discriminant be ∇

Now this polynomial here is positive when t>0 if ∇<0

∇=9Vo^2 * g^2 *sin(θ)^2 -8Vo^2 *g^2

∇<0 ∴ sin(θ)<√(8/9)

Solving for θ

θ<70.53

So i got the maximum value with is 70.53 degrees, what should i do next?