Evaluate :
$\left|\begin{array}{cc}\cos 15°& \sin 15°\\ \sin 75°& \cos 75°\end{array}\right|$

Hi Mehtab, this equals to cos 15 * cos 75 - sin 15 * sin 75
But cos 75 = cos (90 - 15) = sin 15
Same way sin 75 = sin (90 - 15) = cos 15
Thus we have
sin 15 cos 15 - sin 15 cos 15 = 0