The value of `underset(r=0)overset(20)sum(-1)^(r )(.^(50)C_(r))/(r+2)` is equal to

The value of sum_(r=0)^(20)(-1)^(r )(""^(50)C_(r))/(r+2) is equal to

The value of underset(r=1)overset9sum sin^2(rpi)/18 =

The value of .^50c_4+underset(r=1)overset6sum.^(56-r)c_3 is

Prove that the value of underset(r=0)overset10sum cos^3((rpi)/3) is equal to -1/8

Find underset(r=0) overset(10)sumr^ (10)C_(r).3^(r).(-2)^(10-r)

Find the value of underset(r = 0) overset(oo)sum tan^(-1) ((1)/(1 + r + r^(2)))

The value of sum_(r=1)^(n) (-1)^(r+1)(""^(n)C_(r))/(r+1) is equal to

Find the value of underset(r = 1)overset(10)sum underset(s = 1)overset(10)sum tan^(-1) ((r)/(s))

If R_(1) is the circumradius of the pedal triangle of a given triangle ABC, and R_(2) is the circumradius of the pedal triangle of the pedal triangle formed, and so on R_(3), R_(4) ..., then the value of underset( i=1)overset(oo)sum R_(i) , where R (circumradius) of DeltaABC is 5 is