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# stuck on cone question watch

1. i tried to find what L = by doing root 16x^2 + 12x^2 with pythagoras
i then got that 2160pi/pi = 12x (root16x^2+12x^2)
im not to sure if thats right and i dont know what to do next? thanks
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2. (Original post by Gent2324)
i tried to find what L = by doing root 16x^2 + 12x^2 with pythagoras
i then got that 2160pi/pi = 12x (root16x^2+12x^2)
im not to sure if thats right and i dont know what to do next? thanks
You're right so far. You now need to simplify root(16x^2 + 12x^2). 16x^2 + 12x^2 simplifies to 28x^2. What is root(x^2)?
3. (Original post by tiny hobbit)
You're right so far. You now need to simplify root(16x^2 + 12x^2). 16x^2 + 12x^2 simplifies to 28x^2. What is root(x^2)?
so its root 28x^2 which is 2root7x?
4. (Original post by Gent2324)
so its root 28x^2 which is 2root7x?
Yes. You should now be able to solve the equation to find x

Whoops, I wasn't concentrating at the beginning. You didn't square the 16 and the 12 when using pythagoras.
So L^2 = 256x^2 + 144x^2 = 400 x^2 That makes the numbers much easier. I spotted this when I wondered how V was going to turn out to be an integer.
5. (Original post by tiny hobbit)
Yes. You should now be able to solve the equation to find x.
im not to sure how to do that, how do i do 12 times 2root7x?
6. (Original post by Gent2324)
im not to sure how to do that, how do i do 12 times 2root7x?
Go back to the previous post where I explain that I was an idiot. The numbers are now much simpler.
7. (Original post by tiny hobbit)
Go back to the previous post where I explain that I was an idiot. The numbers are now much simpler.
ok so i got 2160pi/pi= 240x because root 400x^2 = 20x and 20x x 12 = 240x, am i suppose to divide 2160pi/pi by 240?
8. (Original post by Gent2324)
ok so i got 2160pi/pi= 240x because root 400x^2 = 20x and 20x x 12 = 240x, am i suppose to divide 2160pi/pi by 240?
It should be 240x^2 as it was 12x (this shows the danger of using x for the letter and for the times sign). Yes divide to get the value of x^2 then square root it.
9. (Original post by tiny hobbit)
It should be 240x^2 as it was 12x (this shows the danger of using x for the letter and for the times sign). Yes divide to get the value of x^2 then square root it.
ah yes i got it now thank you!

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