<p>In page 329, q15.
I’m really confused by their explanation.</p>
<p>I understand that the slope of RS is 1.
But could T be right angle, with RT a slope of 0 and… Well, TS will be undefined. Is this why that is a problem? Because the slope of TS is undefined? </p>
<p>If the slope can’t be undefined, that would make much more sense.
I mean, how do you add an undefined value?..</p>
<p>if T was a right angle, the two sides would have slopes of k and -1/k because, since they enclose a right angle, they are perpendicular and therefore are negative reciprocals of each other.</p>
<p>so k-(1/k)=0 because the sum of the slopes of all 3 sides is 1. since the given side’s slope is 1, the remaining two must add up to 0. 1+0=1</p>
<p>what you are solving for is k. k cannot be 0 because it is in the denominator in the term -1/k.
if it is undefined, then it is not a possible answer in the first place. so obviously you cant add something that isn’t even a possible answer. the possible answers are -1 and 1, which end up being wrong because that would imply that there are 2 sides with slope 1, yet triangles can’t have parallel sides.</p>