Question

1. Determine if each of the following triangles is a right-angled triangle. For each right-angled triangle, state the right angle. (Check attached picture)

The answers are:
(a) Yes; <B
(b) No
(c) No
(d) Yes; <O

I want to know how these answers came, like how can we determine if the triangle is a right-angled triangle or not and which angle is the right angle from the statements in the question. ​

Answer 1

You can use trigonometry specially the cos rule in this case. I can’t send the other pictures. But using the cos rule you can check whether the angle is 90