ac cos B-bc cos A=(a^(2)-b^(2))

2(bc cos A+ca cos B+ab cos C)=a^(2)+b^(2)+c^(2)

D is midpoint of BC in Delta ABC such that AD and AC are perpendicular,Show that cos A cos C=(2(c^(2)-a^(2)))/(3ac)

ABC is a triangle and D is the middle point of BC. If AD is perpendicular to AC, then prove that cos A . cos C =(2(c^(2)-a^(2)))/(3ac)

Prove that in a triangle ABC, bc cos A + ca cos B +ab cos C= 1/2(a^2+b^2+c^2)

In triangle ABC , prove that 2(bc cos A +ac cos B +ab cos C)=a^2+b&2+c^2 .

Prove that: cos^(2)A+cos^(2)B-2cos A cos B cos(A+B)=sin^(2)(A+B)

If alpha and beta satisfy the equation a cos2x+b sin2x=c then prove that (i)cos^(2)alpha+cos^(2)beta=(a^(2)+ac+b^(2))/(a^(2)+b^(2))(ii)cos alpha*cos beta=(a+c)/(2sqrt(a^(2)+b^(2)))

If : A+B+C=pi, "then" : 1-cos^(2) A-cos^(2)B-cos^(2)C= A) 2 cos A * cos B * cos C B) 2 sin A * cos B * cos C C) 2 cos A * sin B * cos C D) 2 cos A * cos B * sin C