R-formula

A ladder of length 10 m rests on a ramp. The vertical height of the top of the ladder above the ground is modeled by
$h = 6\cos\theta + 8\sin\theta$, where $\theta$ is the angle of the ramp. Express $h$ in the form $R\cos(\theta-\alpha)$. What is the value of $\alpha$ (in degrees, to 1 d.p.)?