For the first one, as we know the sum of all three angles of a triangle is always 180°.
- so, since we do not know what is the measure of 3rd angle, let the third angle be x.
- 45 + 45 + x = 18°
- 90 + x = 180°
- x = 180 - 90
- therefore, x = 90°
- Now, we have the value of the third triangle. Now, we need to find the area.
- Area of a triangle = 1/2 × b × h
- = 1/2 × 45 × 90
- = 1/2 × 4050
- = 2025°