Question: show that the RMS value of current

$\displaystyle i = 4sin100 pi T$ is 2.828A

$\displaystyle NOTE: sin^2 theta = 1/2 (1-cos2theta)$

I have tryed to rearange the forumle inorder to work out T

$\displaystyle 4sin 100= i X pi T$

T=4sin 100 i X pi

4sin 100 = 3.939 (2.828 X pi) = 34.99

T=34 but i dont think thats right.

can anyone help me.