Angles in a polygon
Find the sum of the inside angles and the size of each angle in a regular polygon.
A polygon with n sides has inside angles that add up to (n − 2) × 180 degrees. If all the angles are equal (a regular polygon), divide by n to get one angle.
For a hexagon, n = 6: the sum is 4 × 180 = 720 degrees and each angle is 720 ÷ 6 = 120 degrees. Each outside angle is 360 ÷ 6 = 60 degrees.
Classic Graphing 84
Start on the main screen: Press 2nd then mode (QUIT) to get back to the home screen. Pressing clear on a menu also backs out of it.
Type (6 − 2) × 180 and press enter to get the sum, 720.
(6−2)×180enterDivide the last answer by 6. The calculator puts Ans in front for you.
÷6enter
You should see(6−2)*180 720 Ans/6 120
Classic Graphing 84 key reference · Classic Graphing 84 manual
Natural Scientific 991
Start on the main screen: Press MENU, then 1 (Calculate) to return to the main calculation screen. AC clears the line you are on.
Type (6 − 2) × 180 ÷ 6 in one go and press =.
(6−2)×180÷6=
You should see(6−2)×180÷6 120
Natural Scientific 991 key reference · Natural Scientific 991 manual
RPN Scientific 15
Start on the main screen: There is no menu to leave. Press the back arrow to clear a number you are typing, or CLx (g then back arrow) to clear the X register.
Key in 6 ENTER 2 and subtract to get 4.
6ENTER2−Multiply by 180, then divide by 6.
180×6÷
You should see120.0000
Tips
- A triangle (n = 3) gives 180, a quadrilateral (n = 4) gives 360. Use these to check your method.