Originally posted by ^tamago^:
[b]to simplify: sin x/cos²x = (sin x/cos x)*(1/cos x) = sec x tan
x
therefore, d/dx (sec x) = sec x tan x
just to reiteriate...
if the number is a positive integer, then it means power and the
two terms can be used interchangeably, i.e.
cos²x = (cos x)²
cos³x = (cos x)³
if it's -1 it means inverse and not power. i.e. cos¨¹ 60º = acos
60º = 0.5, cos¨¹ 90º = acos 90º = 0
cos¨²x is not meaningful and if u mean the inverse squared, it is
best to use (cos x)¨².
[/b]
Ah i see...thanks 
But i abt blur bout this part..
if it's -1 it means inverse and not power. i.e. cos¨¹ 60º = acos
60º = 0.5, cos¨¹ 90º = acos 90º = 0
y suddenly got 'a' come in one?
