JEE Main201912 Jan 2019Evening ShiftMathematicsDefinite IntegrationActual
lim n → ∞ n n 2 + 1 2 + n n 2 + 2 2 + n n 2 + 3 2 + . . … . + 1 5 n 2 is equal to
Options
- Aπ 4
- Btan - 1 ⁡ 2
- Cπ 2
- Dtan - 1 ⁡ ( 3 )
Correct answer
B. tan - 1 ⁡ 2
Step-by-step solution
To find, lim n → ∞ n n 2 + 1 2 + n n 2 + 2 2 + … + n n 2 + 2 n 2 = ∑ r = 1 2 n n n 2 + r 2 = 1 n ∑ r = 1 2 n 1 1 + r n 2     = ∫ 0 2 1 1 + x 2 d x = tan - 1 ⁡ x 0 2 = tan - 1 ⁡ 2 .