JEE Advance - Mathematics (1998 - No. 30)
Which of the following number(s) is /are rational?
$$\sin {\mkern 1mu} {15^ \circ }$$
$$\cos {\mkern 1mu} {15^ \circ }$$
$$\sin {\mkern 1mu} {15^ \circ }{\mkern 1mu} \cos {\mkern 1mu} {15^ \circ }$$
$$\sin {\mkern 1mu} {15^ \circ }{\mkern 1mu} \cos {\mkern 1mu} {75^ \circ }$$