sec (5/4) to sin

sec = 1/cos   = 5/4

1/(5/4) = cos = 4/5

 

 

cos^2 + sin^2 = 1   (Remember that?)

(4/5)^2 + sin^2 = 1

1-(4/5)^2 = sin^2

9/25 = sin^2

sin = 3/5