Wiskunde Multiple Choice Vraag

Hoeveel correcte gelijkheden staan hier ? \(\small\sin^27^{\circ}+\sin^27^{\circ}.\tan^27^{\circ}\frac{}{}=\tan^27^{\circ}\\\frac{1}{\sin^27^{\circ}}+\frac{1}{\cos^27^{\circ}}\frac{}{}=\frac{1}{\sin^27^{\circ}}\cdot \frac{1}{\cos^27^{\circ}}\\\small\cos^47^{\circ} -\sin^47^{\circ} \frac{\frac{}{}}{}=^{}\cos^27^{\circ} -\sin^27^{\circ} \\\tan^27^{\circ}\cdot \cot7^{\circ}=1\)	A. 1
B. 2
C. 3
D. 4
E. 0

How many correct equalities you find here ? \(\small\sin^27^{\circ}+\sin^27^{\circ}.\tan^27^{\circ}\frac{}{}=\tan^27^{\circ}\\\frac{1}{\sin^27^{\circ}}+\frac{1}{\cos^27^{\circ}}\frac{}{}=\frac{1}{\sin^27^{\circ}}\cdot \frac{1}{\cos^27^{\circ}}\\\small\cos^47^{\circ} -\sin^47^{\circ} \frac{\frac{}{}}{}=^{}\cos^27^{\circ} -\sin^27^{\circ} \\\tan^27^{\circ}\cdot \cot7^{\circ}=1\)	A. 1
	B. 2
	C. 3
	D. 4
	E. 0

\(\sin^2\, 7^\circ+\sin^2\, 7^\circ.\tan^2\, 7^\circ=\sin^2\, 7^\circ(1+\tan^2\;7^\circ)=\sin^2\, 7^\circ.\frac{1}{\cos^2\;7^\circ}=\tan^2\;7^\circ\\\frac{1}{\sin^2\, 7^\circ}+\frac{1}{\cos^2\, 7^\circ}=\frac{\cos^2\, 7^\circ+\sin^2\, 7^\circ}{\sin^2\, 7^\circ.\cos^2\, 7^\circ}=\frac{1}{\sin^2\, 7^\circ.\cos^2\, 7^\circ}=\frac{1}{\sin^2\, 7^\circ}\cdot \frac{1}{\cos^2\, 7^\circ}\)
\(\cos^4\, 7^\circ-\sin^4\, 7^\circ=(\cos^2\,7^\circ-\sin^2\, 7^\circ).(\cos^2\, 7^\circ+\sin^2\, 7^\circ)=\cos^2\, 7^\circ-\sin^2\, 7^\circ\\\tan^2\, 7^\circ\cdot \cot^2\, 7^\circ=1 \)