Hi

Upon checking an intergral (that I had worked out by hand) using mathcad(some math software I have) I noticed a simplification of part of my intergral the computer had performed and couldnt work out how it was made.

it is

-sec(6pi/8) = sqrt(2)

I was wondering if anyone knows how one gets from one to the other ?

I have even checked with my my tutor and he isnt sure either !

is there some identity I am not aware of ?