Thread: Simplifying a fraction in trig

1. Simplifying a fraction in trig

Hi all, this is my first post and I feel like I shouldn't even have to ask, but I'm having a tough time figuring this out. I watched an instructional video teaching how to solve for the arc of an angle and in the video, he divides a fraction and gets another fraction. My issue is I have no idea how he got the resulting fraction...

25pi/8 = 4.8a
125pi/192 = a

How does it simplify into a much larger number? According to the algebra I know, it's supposed to come out to 25pi/38.4 = a. What am I missing?

Thanks!

2. Re: Simplifying a fraction in trig

Hi noamo48,

Instead of keeping 4.8 in decimal form, the video you watched used 4.8 = 24/5 (without saying it explicitly). If instead we write $\frac{25\pi}{8}=\frac{24a}{5},$ can you see how they got the final answer?

Let me know if anything is unclear. Good luck!

3. Re: Simplifying a fraction in trig

great, i knew i'd feel dumb for asking. thanks!

4. Re: Simplifying a fraction in trig

One can also get the same result by just cross multiplication.
25 pi/8 = 4.8 a that gives a = [25pi/8 ] [ 1/(4.8)] = [25pi/8 ] [ 10/48]= [25pi/8 ] [ 5/24]= 125pi/192
In fact I recommend this method for it is simple and appears logical to me.