Everyone in my math class (including the teacher) is having problems with this trigonometry question: 
I am assuming that you halve the pendulum and the bottom of the triangle would be $\frac{1.8}{2} = 0.9$. Then using $\tan$ you can figure out the rise of the pendulum like below (where $x$ is equal to the rise)?
$$
\tan (24) = \frac{x}{0.9} \\
\frac{0.4452}{1} = \frac{x}{0.9} \\
x = 0.4452 \times 0.9 \\
x = 0.4007 \\
x \approx 0.401
$$
Please let me know if this is right or if I am doing it totally wrong (which I think I am).
Best Answer
If the length of the pendulum string is $L$ and the string makes an angle $\theta$ with the vertical, then the vertical distance (from anchor point of the string down the the height of the bob) is $$ L \cos \theta. $$ (Do you see why?)
Now, the height of the bob, measured up from the lowest point is $$ h = L - L \cos \theta = L(1 - \cos \theta). $$
Now, plug in $L = 1.8$m and $\theta = 24^{\circ}$ to find $h$.