McGraw-Hills 10 ACT book is the worst... can someone explain this to me?

Test Preparation ACT Preparation
1

<p>So today I was doing the math section, and I came across this problem. </p>

<p>View</a> image: act math</p>

<p>Basically, it gave one angle and its corresponding side and said the triangle was isoceles.</p>

<p>Since the angle is 40 degrees and the other two sides are isoceles, the other two angles opposing the equal sides are both 70 degrees (sorry if I'm not explaining this well enough, but you probably get what I mean).</p>

<p>Anyways, I had to find another side, so I thought oh SINE RULE</p>

<p>couldn't get the right answer so I left it, came back at the end and checked the book.
View</a> image: math explanation </p>

<p>Why on earth would you do it like that?</p>

<p>Wouldn't you do 5/sin40=XY/sin70?? Or have my trig years failed me....</p>

2

<p>that exactly what i did.
i thought i was maybe wrong so i also tried another way so i made it an right angle(dropped an angle bisector down from angle A) and then you get the base to be 2.5 the angle as 20 and the hypotenuse as x so we have sin 20 = 2.5 / x
and x = 7.3 approx. same as the answer i got from law of sines.</p>

3

<p>well i just realized that the law of sines and the way the book did cant both be right…
if i had to, i’d pick law of sines…</p>

4

<p>this suggested answer has to be wrong!!</p>

5

<p>On the ACT, they will always give you the formula for Law of Sines or Law of Cosines if you are required to use it.</p>

<p>Non-ACT published books are always problematic. Some are rife with errors while others are less conspicuously wrong. I always urge students to tread with caution when purchasing non-official prep material.</p>

6

<p>The answer is wrong. Instead of doing YZ/sinX=XY/sinZ=XZ/sinY, they did YZ/angleX=XY/angleZ=XZ/angleY. They left out all the “sin” in the Law of Sines.</p>

7

<p>Okay that’s great to hear. Yeah this book is filled with errors (I’ve found at least 1 or 2 math ones, a few writings ones, and a few science ones).</p>