1another one:
5 Answers
11. det = sinA(cosB - cos C ) - sin B ( cos A - cos C) + sin C ( cos A - cos B)
=sin A cos B - sin A cos C - sin B cos A + sin B cos C + sin C cos A - sin C cos B
= ( sin A cos B - sin B cos A) + ( sin B cos C - sin C cos B) + (sin C cos A - sinA cos C)
= sin ( A - B) + sin (B - C) + sin (C - A)
since ABC is scalene => A-B , B-C , C- A are not equal to zero
=> det is not equal to zero
12 . doing the reverse of the question
since triangle is isoceles A= B
hence determinant value becomes 0
1thanks madhu and omkarsatish.
they are easier than they seemed![1]
btw,is there any other method except proceeding from backwards for 2nd ques?
