MathDB
Problems
Contests
National and Regional Contests
Indonesia Contests
Indonesia MO
2016 Indonesia MO
4
4
Part of
2016 Indonesia MO
Problems
(1)
Equation with cosinus
Source:
10/28/2017
Given triangle
A
B
C
ABC
A
BC
such that angles
A
A
A
,
B
B
B
,
C
C
C
satisfy
cos
A
20
+
cos
B
21
+
cos
C
29
=
29
420
\frac{\cos A}{20}+\frac{\cos B}{21}+\frac{\cos C}{29}=\frac{29}{420}
20
cos
A
+
21
cos
B
+
29
cos
C
=
420
29
Prove that
A
B
C
ABC
A
BC
is right angled triangle
geometry
algebra
Trigonometric Equations