Question

write as an algebraic expression cos(sin^-1x)

Answer 1

I dont understand what you want :S

Answer 2

you can start by putting y = sin^-1 x
then
x= sin y
and you'll need cos y

Answer 3

can you think of next step ?

Answer 4

cos (sin^-1 x) = cos y = sqrt (1- sin^2 y)
but sin y = x !
so,
cos (sin^-1 x) = sqrt (1- x^2)
thats it!