In any triangle ABC, prove that:
(i) a = b cos C + c cos B (ii) b = c cos A + a cos C (iii) c = a cos B + b cos A
Let I be incentre of the triangle ABC
Join ID, IE and IF which are perpendicular to BC, CA and AB respectively
ID = IE = IF = r (In radius)
Now, area of the triangle ABC =
= Area of triangle IBC + Area of triangle ICA + Area of triangle IAB
or