Question 612310
{{{ cos^-1 (sqrt ( 3 )/2) }}}
This expression represents: "the angle, between 0 and {{{pi}}}, whose cos is {{{sqrt(3)/2}}}".<br>
If you know your special angle values, then you know that the reference angle for angles with this cos is {{{pi/6}}}. While there are an infinite number of angles with a cos of {{{sqrt(3)/2}}} [{{{pi/6}}}, {{{-pi/6}}}, {{{13pi/6}}}, {{{-13pi/6}}}, {{{25pi/6}}}, etc.], there is only one angle between 0 and {{{pi}}}: {{{pi/6}}}