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Math Help - Simplifying a fraction in trig

  1. #1
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    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...

    The expression was this (a = angle):
    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!
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  2. #2
    GJA
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    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!
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  3. #3
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    Re: Simplifying a fraction in trig

    great, i knew i'd feel dumb for asking. thanks!
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  4. #4
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    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.
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