The sum of seven of the angles of a decagon is 1170°. The other angles are equal to each other. Calculate the size of the 3 angles.
The sum of the angles of a decagon is 1440° (n-2) x 180, where n is the number of sides.
Let x be the measure of each of the three equal angles.
We know that the sum of seven angles is 1170°, so the sum of the remaining three angles is:
1440° - 1170° = 270°
Since the angles are equal, we can write:
3x = 270°
Dividing both sides by 3, we get:
x = 90°
Therefore, each of the three equal angles is 90°.