The vertices of a regular polygon of 12 sides are joined to form triangles. The number of triangles which do not have their sides as the sides of the polygon is
11
TotalNo.ofΔles=12C3=220
No.ofΔleswith two sides common with polygon=12
No.ofΔles with all side common=8.12=96
∴ans=220−(12+96)=112