vikas askiitian expert
Last Activity: 14 Years ago
a2+b2+c2 = ab+bc+ac (given)
cosA = b2+c2-a2/2bc
2bccosA = b2+c2-a2 ...........1
2accosB = a2+c2-b2 ..........2
2abcosC = a2+b2-c2 .........3
adding 1,2,3
2(abcosC+bccosA+accosB) = a2+b2+c2 ........4
a2+b2+c2 = ab+bc+ac (given)
so , 2(abcosC+bccosA+accosB) = ab+bc+ac
2ab(cosC-1/2) + 2bc(cosA-1/2) + 2ac(cosB-1/2) = 0
from this eq , cosC = cosA = cosB = 1/2
A=B=C = Pi/3
so the triangle is equilateral , acute angled triangle...
approve if u like my ans