<p>I have a question about problem #19 on page 401. I can't summarize the whole problem here because it would be hard for me to do, so I hope you guys can take the liberty of flipping to that page in the book - it'd mean a lot. So, the answer to the problem is choice (A) which I do understand after reading the CB's explanation on their site. </p>
<p>Their explanation: P = the point where the altitude meets the base of the pyramid.
Q = any vertex of the base.
Draw a line from P to Q, and you get a triangle. Now you must assume that PQ is half the length of the diagonal of the base, and from this, you get the length of PQ and are able to solve for the answer using Pythagorean Theorem. I completely understand this, but instead of doing that, what if I drew a segment from point P to the midpoint of any side of the base. If I did that, I could have simply assumed that the segment I drew is half of m, correct? According to the CB, I can't do so.... why not?</p>
<p>I know what I wrote seems like jibberish, but if you do the problem, you'll see what I mean!</p>