# Thread: projectiles

1. ## projectiles

the equation of a projectile can be written as
(i)show that the point can be hit by firing at two different angles and if
(ii) show that no point ABOVE the x axis can be hit by firing at two different angles such that and
i have completed part one but i have no idea how to approach part two

2. Originally Posted by calculus_jy
the equation of a projectile can be written as
(i)show that the point can be hit by firing at two different angles and if
(ii) show that no point ABOVE the x axis can be hit by firing at two different angles such that and
i have completed part one but i have no idea how to approach part two
The second part is asking you to show that the equation:

$y=x \tan(x) - \frac{1}{4h}x^2(1+\tan^2(x))$

has no (real) roots for $x$ when $\theta$ in the given range for any positive $y$.

As this is a quadratic in $x$ you examine the discriminant.

RonL