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2016 Postal Coaching
1
Angles of ABC in decagon
Angles of ABC in decagon
Source: India Postal Set 6 P1 2016
January 18, 2017
geometry
Problem Statement
Let
A
1
A
2
A
3
⋯
A
10
A_1A_2A_3\cdots A_{10}
A
1
A
2
A
3
⋯
A
10
be a regular decagon and
A
=
A
1
A
4
∩
A
2
A
5
,
B
=
A
1
A
6
∩
A
2
A
7
,
C
=
A
1
A
9
∩
A
2
A
10
.
A=A_1A_4\cap A_2A_5, B=A_1A_6\cap A_2A_7, C=A_1A_9\cap A_2A_{10}.
A
=
A
1
A
4
∩
A
2
A
5
,
B
=
A
1
A
6
∩
A
2
A
7
,
C
=
A
1
A
9
∩
A
2
A
10
.
Find the angles of the triangle
A
B
C
ABC
A
BC
.
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