Icosagon

[iren.perch]

In the regular twenty angle(icosagon) GHIJ. . . XYZ are the names of the angles in alphabetical order.
Angle JWO + VWO equals...
If I'm right each angle is (20-2)x180/20=162 degrees.
But I do not know how I should calculate the rest.
Can someone help me?
Thank you in advance.

 

[Dr.Peterson]

How many edges are there between J and O? How many between V and O? What does that tell you about each angle, JWO and VWO?

Please also explain what "each angle" refers to, and where 20-2 comes from, just to make sure we're on the same page. I think you're looking at interior angles of the polygon; I'd focus more on the central angle subtended by each edge, though there are other ways.

 

[firemath]

Your measure for the internal angles was correct.
Here is a visualization:

Purple=O
Black=V
Blue=J
Green=W

 

[iren.perch]

Thank you all!
I worked with a circle:
360:20=18
18*7=126
18*5=90
126+90=216
216/2=108 degrees

 

[Dr.Peterson]

Perfect.

To put it another way, there are 12 sides between J and V, the angle at W between any two adjacent vertices is 9 degrees, and 12 times 9 is 108 degrees.