Question 1077791

Bob was standing in front of tall building. As he moves 75 feet closer to the building, his angle of elevation changes from 20 degree to 35 degree. What is the height of this building?
Please help me to solve this. Thanks. 
<pre><b><sup>1)</b></sup> Use distance he traveled to get closer (75'), the original angle of elevation (20<b><sup>o</b></sup>), the difference between the angles of elevation 15<b><sup>o</b></sup> (35<b><sup>o</b></sup> - 20<b><sup>o</b></sup>),
   and the law of sines to get the length of the hypotenuse of the triangle, formed from his current distance from the building and the height of the building.
   This should be: {{{matrix(1,2, 99.10983, feet)}}}   
<b><sup>2)</b></sup> Use the length of the hypotenuse above (99.10983 feet), along with the 35<b><sup>o</b></sup> &#8736, and the SINE ratio to get the height of the building. 
   This should be: {{{highlight_green(matrix(1,2, 56.84706, feet))}}}