Tm denotes the number of triangles that canbe formed with the vertices of a regular polygon of m sides. If Tm + 3 - Tm = 15, then m is equal to
3
6
9
12
If the coefficients of x9, x10 and x11 in the expansion of (1 + x)n are in arithmetic progression, then n2 - 41n is equal to
399
298
- 398
198
If sin(A) + sin(B) + sin(C) = 0 and cos(A) + cos(B) + cos(C) = 0, then cos (A + B) + cos (B + C) + cos(C + A) is equal to
cos(A + B + C)
2
1
0
If , then is equal to
A.
The arithmetic mean of the observations 10, 8, 5, a, b is 6 and their variance is 6.8, then ab is equal to
6
4
3
12