Question
In a ΔABC,a(b cosC −c cos B) is equal to -
Answer: Option C
:
C
We know from cosine rule
cosC=a2+b2−C22ab
cosB=a2+c2−b22ac
So we'll use these in the given expression.
a{b(a2+b2−c22ab)−c(a2+c2−b22ac)}
a2+b2−c2−a2−c2+b22
=2(b2−c2)2
=b2−c2
Was this answer helpful ?
:
C
We know from cosine rule
cosC=a2+b2−C22ab
cosB=a2+c2−b22ac
So we'll use these in the given expression.
a{b(a2+b2−c22ab)−c(a2+c2−b22ac)}
a2+b2−c2−a2−c2+b22
=2(b2−c2)2
=b2−c2
Was this answer helpful ?
Latest Videos
Latest Test Papers
Submit Solution