Questions in trigonometry

Select	Question
	Which of the following number(s) is/are rational
	$\cos 15{}^\circ =$
	If $\sin A+\cos A=\sqrt{2},$then ${{\cos }^{2}}A=$
	$2{{\cos }^{2}}\theta -2{{\sin }^{2}}\theta =1$,then $\theta =$
	If $\sin \alpha =\frac{336}{625}$and $450{}^\circ <\alpha <540{}^\circ ,$ then $\sin \left( \frac{\alpha }{4} \right)=$
	If ${{\tan }^{2}}\theta =2{{\tan }^{2}}\varphi +1,$ then $\cos 2\theta +{{\sin }^{2}}\varphi $ equals
	$\cos ^4 \frac{\pi}{8} + \cos ^4 \frac{3 \pi}{8} + \cos ^4 \frac{5 \pi}{8} + \cos ^4 \frac{7 \pi}{8} =$
	If $\sin x+\cos x=\frac{1}{5},$then $\tan 2x$is
	${{\cos }^{2}}A{{(3-4{{\cos }^{2}}A)}^{2}}+{{\sin }^{2}}A{{(3-4{{\sin }^{2}}A)}^{2}}=$
	$\frac{\tan A+\sec A-1}{\tan A-\sec A+1}=$