(Q). Consider a square along with its 2 diagonal. How many triangle is formed by this system?
Solution:-
total vertices i.e. total points = 5
∴ if no three point would have collinear then number of triangle = ⁵C₃
Since there are 2 sets of three collinear points
hence required number = ⁵C₃ – 2׳C₃
= 10 – 2
= 8 Answer