bumblebee123
Junior Member
- Joined
- Jan 3, 2018
- Messages
- 200
can anyone help me with this?
question: the sizes of the interior angles of a non-regular pentagon ABCDE form an arithmetic sequence. Prove that one of the interior angles of ABCDE must be 108 degrees
here's what I know:
all interior angles of a pentagon add up to 540 degrees.
Sn = n/2 [ 2a + ( n - 1)d ]
S5 = 2.5 [ 2a +4d ]
S5 = 5a + 10d
540 = 5a + 10d
exterior angles of any polygon add up to 360 degrees
any suggestions about what to do next would be highly appreciated!
question: the sizes of the interior angles of a non-regular pentagon ABCDE form an arithmetic sequence. Prove that one of the interior angles of ABCDE must be 108 degrees
here's what I know:
all interior angles of a pentagon add up to 540 degrees.
Sn = n/2 [ 2a + ( n - 1)d ]
S5 = 2.5 [ 2a +4d ]
S5 = 5a + 10d
540 = 5a + 10d
exterior angles of any polygon add up to 360 degrees
any suggestions about what to do next would be highly appreciated!