1. Fie a, b , c si d masurie unghiurilor patrulaterului.
a + b + c + d = 360
a/2 = b/5 = c/7 = d/10
b = 5a/2
c = 7a/2
d = 10a/2 = 5a
a + 5a/2 + 7a/2 + 5a = 360
6a + 12a/2 = 360
6a + 6a = 360
12a = 360
a = 360:12 = 30°
b = 5×30/2 = 75°
c = 7×30/2 = 105°
d = 5×30 = 150°
2. a/1 = b/2 = c/3 = d/4
a + b + c + d = 360
b = 2a
c = 3a
d = 4a
a + 2a + 3a + 4a = 360
10a = 360
a = 36°
b = 72°
c = 108°
d = 144°