Q16Short answer
Show that the ∆ABC is an isosceles triangle if the determinant DETERMINANTS 79 1 1 1 ∆ = 1 + cos A 1 + cos B 1 + cos C = 0 . cos 2 A + cos A cos 2 B + cos B cos 2 C + cos C 0 1 1 A 2 − 3I Find A if A = 1 0 1 and show that A = –1 –1