Explanation for Question 18 From the Math (No Calc) Section on the 2020 October Sat
So question 18 tells us that we have two triangles, 2 ABC, a DBE, and both of them are right triangles, 3 which we know because of this little box here. 4 And it wants to know what is the co-sign of B first thing we 5 can do is find a, will be an angle B is right here. 6 And so now we have to ask ourselves, okay, what is co-sign if we 7 think back to sohcahtoa, we know that co-sign is adjacent over hypotheses. 8 And now the important thing to remember here is that B is inside of 9 both triangles is inside a little, little triangle that's right here. 10 And then it's inside of the bigger triangle that kind of encompasses the little 11 triangle. And so the easiest thing to do is only focus on the little 12 triangle, because those are the side blanks that we actually have. 13 And if I look at the side, that's adjacent to B, it's going to 14 be six, because six is the side length, 15 the height, I guess, of the little triangle. 16 And then the hypotony use of the little triangle is 10. 17 So 10 is my adjacent over my news. 18 And then I can simplify by dividing both by two. 19 So I get three over five and three over five will be my co-sign 20 of beat.