What is wrong in my solution attempt to the $80^\circ$-$80^\circ$-$20^\circ$ problem?

Question

I'm trying to solve the following famous problem:

Here's my attempt, for some reason it leads to a contradiction, where have I gone wrong?

Please do not give me any hints on how to solve the problem on a whole, as I want to solve it on my own. If I'm wrong I'll try another approach, but I'd like to know where I have went wrong.

70 is easily 180 - 50 - 60, and by that you can get the 4 angles in the middle (70, 110, 70, 110) ----- then you can use that the angles of the triangle sum to 180 to get the remaining — ArandomUserNameEG, Nov 29 '17 at 17:18
Looks like you made a simple mistake when hunting for the angles in your first diagram implication. — Jacky Chong, Nov 29 '17 at 17:27
When you are interested in a full solution, visit this question. — Blue, Nov 29 '17 at 21:41

D.R. · Answer 1 · 2017-11-29T17:17:33.833

3

The angle at the top of the triangle is not $40^\circ$.

edited Nov 29 '17 at 17:17

answered Nov 29 '17 at 17:16

D.R.

10,556

Shouldn't it be 180 - (The 2 bottom angles) = 40? – ArandomUserNameEG Nov 29 '17 at 17:17
1

The two bottom angles sum to $80+80=160$, if I'm not mistaken – D.R. Nov 29 '17 at 17:18
1

ugh such an amateur mistake rip my bad – ArandomUserNameEG Nov 29 '17 at 17:19

score 3 · Accepted Answer · answered Nov 29 '17 at 17:18

3

Angles B and C equal 80 degrees each. with angle A equaling 40 degrees, the sum of degrees is 200, not 180.

answered Nov 29 '17 at 17:18

Ult1m8_n00b

46

What is wrong in my solution attempt to the $80^\circ$-$80^\circ$-$20^\circ$ problem?

2 Answers2