Inverse of a function help

[Sin]

I need some help with a certain problem.
The question is:

http://puu.sh/2tPv6

Where I is a certain angle, and n is the number of sides.
I have to find the number of sides a polygon has by using the given angle (108). (Just have to sub 108 into I)

I got the answer:
http://puu.sh/2tPHP
as the inverse

However, this equation also results in the correct answer:
http://puu.sh/2tPxV

The correct answer is 5/Pentagon.
Are they both right? Am I wrong?

[Nebula]

Correct way to solve: http://puu.sh/2tQch

yours is wrong

[[XoL]]

Solve for n:
(180 (n-2))/n = i
Multiply both sides by a polynomial to clear fractions.
Multiply both sides by n:
180 (n-2) = i n
Write the linear polynomial on the left hand side in standard form.
Expand out terms of the left hand side:
180 n-360 = i n
Isolate n to the left hand side.
Subtract -360+i n from both sides:
(-i+180) n = 360
Solve for n.
Divide both sides by 180-i:
Answer: |
| n = (360 i)/32401+64800/32401

On my phone doing wolfram

[masterBB]

http://i.imgur.com/vHrPIlE.png

[Enslaved]

masterBB , what software do you use for visulisation or do u use mathML/LaTeX

[masterBB]

masterBB , what software do you use for visulisation or do u use mathML/LaTeX

People ask me that a lot. I simply use Microsoft Word.

[Richard]

Sin, you're making the mistake of thinking you need to form the inverse of the function, which you don't need to do at all. When you inverse a function, it actually become an entirely different thing (it's actually a reflection in y=x).

What you need to do is simply sub the value of i in:

108 = 180 - 360/n
-72 = -360/n (minus 180)
-72n = -360 (time by n)
-n = -5 OR n = 5 (divide by 72 [or -72])

[Sin]

Damn <.<
Gg 2marks..