If cos2A + cos2B + cos2C = 1 then ABC is a
(a) Right angle triangle
(b) Equilateral triangle
(c) All the angles are acute
(d) None of these

• (a)right angle triangle
• 10 years agoHelpfull: Yes(0) No(0)
• Two of the angles must be complements of each other. The third angle will be a right angle (90°). The equation is symmetrical in all of the variables, so you can choose angle A to be anything you like in the range 0 to 90°. so its Right angle triangle
• 10 years agoHelpfull: Yes(0) No(0)