Explanation for Question 15 From the Math (Calc) Section on the 2019 October Sat
Now number 15, we're told that we have a triangle triangle, 2 a B, C, or a 50 degrees, 3 and then it tells us that triangle, ABC is isosceles, 4 which of the following is not a possible angle measure of B. 5 So if we're told that this triangle has to be isosceles, 6 there are really two ways we can think about it, right? 7 Either angle a could be congruent angle C that would allow a triangle to 8 be isosceles. Um, because then I saw Louise has two congruent angles 9 and two congruent sides. So 10 that's one option where the A's and the C's are congruent. 11 And another option. Draw it a little bit differently here. 12 Okay. BC, we could have the a and the B being congruent, 13 right? And then the C is kind of on its own. 14 And so it's possible here that B could be 50 degrees and that would 15 allow our triangle to be isosceles. 16 And since we want angle measure, that's not possible a is not going to 17 work here. Right. And so now we can think about what could possibly 18 be an angle B right here. 19 Um, and we can do that first by taking 180 and subtracting, 20 um, 50 minus 50, 21 because this is angle a, and this is angle C and all of our 22 angles should add up to 180 and 180 minus 50 minus 50. 23 That means the angle B could be 80 degrees. 24 Right? And so it is also possible that B is 80. 25 And so we have to eliminate that answer choice. And now the final thing 26 is, could the angle be 65 degrees or could it be 100 27 degrees? Um, and so let's take a look here, 28 ri...