Posted by Anonymous on Saturday, November 7, 2009 at 10:19pm.
Show that
sinx = (square root of) 1  cos^2x
is not an identity

Math  Reiny, Saturday, November 7, 2009 at 10:40pm
All we need is one counterexample to show it is not an identity.
let x = 210º
LS = sin 210 = 1/2
RS = √(1 cos^2 (210º))
= √(.25)
= 1/2
So there!