Square root

In mathematics, the value of the square root of negative one was i, an imaginary number. (AUDIO: Iterations of I)

The square root of pi was 1.772453850905516027298167483341. The Tenth Doctor used that sequence to test the intelligence and memory retention of the Midnight entity. (TV: Midnight)

The square root of 17422 was 131.993. The First Doctor asked WOTAN this question to demonstrate its power. (TV: The War Machines)