With usual notations, is a △ABC b2−c2a sec c + c2−a2b sec c + a2−b2c sec c is equal to
1
0
abc
None of these
We have b2−c2a.cosA + c2−a2b.cosB + a2−b2c.cosC =b2−c2a.b2+c2−a22bc + c2−a2b.c2+a2−b22ac+a2−b2b.c2+a2−b22ac =0
If a=cos α cos β+sin α sin β cos γ, b=cos α sin β−sin α cos β cos γ and c=sin α sin γ then a2+b2+c2 is equal to
In any △ABC, 1r21+1r22+1r23+1r2 is equal to