## anonymous one year ago i'll medal and fan for some trig help :)

1. johnweldon1993

Whatcha need help with? :)

2. anonymous

hi! @johnweldon1993 I'm reviewing for my final for my summer course but misplaced my notes on internal and external angles and have a couple questions about it

3. johnweldon1993

4. anonymous

so im trying to find the sum of interior angles of a decagon, and if im remembering correctly, the formula is (n-2)180 n being the number of sides

5. johnweldon1993

Correct :) And since we know that a decagon has 10 sides, we just replace 'n' with 10 and evaluate

6. anonymous

soooo (10-2)180 --> (8)180=1440?

7. johnweldon1993

Correct indeed :)

8. anonymous

ok, i have a couple more questions is that ok? :)

9. johnweldon1993

of course :)

10. anonymous

ok so if each exterior angle is 12 degrees, how many sides does the polygon have? I forget this formula :(

11. johnweldon1993

Well we can remember the formula in the sense that ALL polygons have exterior angles that add to 360 So in order to find out how many sides we can use the fact that $\large \frac{360}{\text{number of sides}} = \text{length of each side}$

12. johnweldon1993

Did that make sense? :)

13. johnweldon1993

Sorry, should have said "measure of each exterior angle" as opposed to "length of each side" kinda confusing context there...sorry about that