In triangle ABC, D is the mid point of BC. If AD is the perpendicular to AC, then cosAcosC= ?

[1] 2(c²+a²) / 3ac

[2] (c²-a²) / 3ac

[3] 3(c²+a²) /3ac

[4] 2(c²-a²) /3ac

Shubhashish singh

10 Years agoGrade 11