Projectile Motion - Arrow

In a 2D game, I simply want to draw the trajectory of an arrow in flight. With the code below, the trajectory (the parabola) looks right, but the angle (or rotation) or the arrow isn't.

float g = -9.8f;
float x = (launchVelocity * time);
float y = (launchVelocity * time) + (0.5f * g * (float)Math.Pow(time, 2));
float angle = (float)Math.Tanh(y / x);

What am I missing? Thanks.