What is the value of #sin(arcsec(x/3))#?

1 Answer
Sep 1, 2017

It can be simplified to #|sqrt(x^2 -9)/x|#

Explanation:

If we let:

#theta = arcsec(x/3)#

Then

#sectheta = x/3#

Since #sectheta# by definition is defined by #"hypotenuse"/"adjacent"#, we know the hypotenuse measures #x# and the side adjacent measures #3#. This means that the side opposite #theta# measures #sqrt(x^2 - 9)#.

Furthermore, #sintheta = sqrt(x^2 - 9)/x#.

Therefore, the expression in question can be simplified to

#sin(arcsec(x/3)) = sin(theta) = sqrt(x^ 2 - 9)/x#.

But if we observe the graph of #f(x) = sin(arcsec(x/3))#, we notice that #y> 0#. So the correct answer is #sin(arcsec(x/3)) = |sqrt(x^2 -9)/x|#.

Hopefully this helps!