AP EAMCET Engineering 23 Apr 2019 Shift 1 Paper

The complex conjugate of the given points are in arg and plane A(1−2i),B+(2+3 i),C(3+4i)
So,
a=BC
=√1+1
=√2
And,
b=CA
=√4+36
=√40
And,
c=AB
=√1+25
=√26
This implies,
cos‌B=

a2+c2−b2

2ac

=

2+26−40

2√2√26

=−

12

4√13

=−

3

√13

<0
So, the points A, B, C represent vertices of an obtuse triangle.