MathDB
Problems
Contests
National and Regional Contests
Moldova Contests
Chisinau City MO
1949-56 Chisinau City MO
59
Chisinau MO p59 1949-56 X cos ^2 A + cos ^2 B + cos ^2 C=1
Chisinau MO p59 1949-56 X cos ^2 A + cos ^2 B + cos ^2 C=1
Source:
March 15, 2021
trigonometry
right triangle
geometry
Problem Statement
Show that triangle
A
B
C
ABC
A
BC
is right-angled if its angles satisfy the ratio
cos
2
A
+
cos
2
B
+
c
o
s
2
C
=
1
\cos^2A + \cos ^2B +\ cos ^2C=1
cos
2
A
+
cos
2
B
+
co
s
2
C
=
1
.
Back to Problems
View on AoPS