`sum_(i=1)^ootan^(- 1)(1/(2i^2))=t ,then tant=`

The sum sum _(n=1)^ootan^(-1)(1/(2^n+2^(1-n))) equals

The value of sum_(m=1)^ootan^(- 1)((2m)/(m^4+m^2+2)) is

If sum_(i=1)^(15)x_(i)=45,A=sum_(i=1)^(15)(x_(i)-2)^(2) , B=sum_(i=1)^(15)(x_(i)-3)^(2) and C=sum_(i=1)^(15)(x_(i)-5)^(2) then Statement 1: min(A,B,C)=A Statement 2: The sum of squares of deviations is least when taken from man.

If sum_(i=1)^n(x_i+1)^2=9n and sum_(i=1)^n(x_i-1)^2=5n , then standard deviation of these 'n' observations (x_1) is: (1) 2sqrt(3) (2) sqrt(3) (3) sqrt(5) (4) 3sqrt(2)

If sum_(i=1)^(5) (x_(i) - 6) = 5 and sum_(i=1)^(5)(x_(i)-6)^(2) = 25 , then the standard deviation of observations

If sum_(i=1)^(9) (x_(i)-5) " and" sum__(i=1)^(9) (x_(i)-5)^(2)=45 , then the standard deviation of the 9 items x_(1),x_(2),..,x_(9) is

If (a_(1)+ib_(1))(a_(2)+ib_(2))………………(a_(n)+ib_(n))=A+iB , then sum_(i=1)^(n) tan^(-1)(b_(i)/a_(i)) is equal to

If sum_(i=1)^(7) i^(2)x_(i) = 1 and sum_(i=1)^(7)(i+1)^(2) x_(i) = 12 and sum_(i=1)^(7)(i+2)^(2)x_(i) = 123 then find the value of sum_(i=1)^(7)(i+3)^(2)x_(i)"____"

If sum_(i=1)^(18)(x_(i) - 8) = 9 and sum_(i=1)^(18)(x_(i) - 8)^(2) = 45 then find the standard deviation of x_(1), x_(2),….x_(18)

If for a sample size of 10 , sum_(i=1)^(10)(x_i-5)^2=350 and sum_(i=1)^(10)(x_i-6)=20 , then the variance is