For what value(s) of x, 0<x<pi/2, is sinx<cosx
If you have a graphing calculator and any hesitation at all about this, the best way to go is to graph. Make sure your calculator is in radians mode!
Between and
, the red
curve is below the blue
curve until
. After that point, the lines cross.
Without a calculator, you should still be able to reason this one out if you remember a few basics:








From the above, you know that the cosine curve is higher than the sine curve at , and that the curves intersect at
. They don’t intersect again before
.