Question

In a triangle ABC, D is the mid-point of BC and AD ⟂ AC. Then which of the following is true (a, b, c are sides of ΔBAC as usual):

(a)  3b² = a² + c²

(b)  2b² = a² + c²

(c)  3b² = a² - c²

(d)  2b² = a² - c²

Answer 1

Correct option (c)  3b² = a² - c²

See Fig.

 sine rule for a ∆.

⇒ 3b² = a² - c²