The given triangle is a right-angled triangle. This means that special trig identities can be applies
<u>These identities are as follows:</u>
sin (theta) = opposite / hypotenuse
cos (theta) = adjacent / hypotenuse
tan (theta) = opposite / adjacent
<u>Now, for the unknown theta in the triangle:</u>
The opposite side is 16 and the hypotenuse is 20
This means that we will use the <u>sin</u> not the cos as Bob did
<u>The solution will be as follows:</u>
sin (theta) = opposite / hypotenuse
sin (theta) = 16 / 20
theta = sin^-1(16/20)
theta = 53.13°
Hope this helps :)
