Angles in a triangle, step by step
Every triangle's three angles come to 180°, and that one fact answers every question on these sheets.
The question
degrees
The third angle, given 35° and 40°
3 corners=a straight line=180°
35 + 40 =75
35 + 40 =75
180 − 75 =105°
- Every triangle's three angles add to 180 — and that is not a number to take on trust. Tear the three corners off any triangle you like and they fit together into a straight line, every time.
- Two of them are given: 35 and 40, which is 75 between them.
- So the third takes up what is left of the 180: 180 − 75 = 105°.
How it works.
- 01
Every triangle's three angles add to 180 — and that is not a number to take on trust. Tear the three corners off any triangle you like and they fit together into a straight line, every time.
- 02
Two of them are given: 35 and 40, which is 75 between them.
- 03
So the third takes up what is left of the 180: 180 − 75 = 105°.