It appears that you correctly used the Pythagorean Theorem to find $\displaystyle{h}=\sqrt{{34}}\usepackage{cmbright}\Huge\$ , but you found the value of $\displaystyle{\sin{\theta}}\usepackage{cmbright}\Huge\$ . Remember the definition is:

$\displaystyle{\cos{\theta}}=\frac{\text{adjacent}}{\text{hypotenuse}}\usepackage{cmbright}\Huge\$