[tex]\begin{gathered} \frac{1+\tan^2(u)}{1-\tan^2(u)}=\frac{1+\frac{\sin^2(u)}{\cos^2(u)}}{1-\frac{\sin^2(u)}{\cos^2(u)}} \\ \\ \end{gathered}[/tex]
Fill first blank with:
[tex]\sin ^2(u)[/tex][tex]\frac{1+\frac{\sin^2(u)}{\cos^2(u)}}{1-\frac{\sin^2(u)}{\cos^2(u)}}\times\frac{\cos^2(u)}{\cos^2(u)}=\frac{\frac{\cos ^2(u)+\sin ^2(u)}{\cos ^2(u)}\times\cos ^2(u)}{\frac{\cos ^2(u)-\sin ^2(u)}{\cos ^2(u)}\times\cos ^2(u)}=\frac{\cos ^2(u)+\sin ^2(u)}{\cos ^2(u)-\sin ^2(u)}[/tex]
Fill second blank with:
[tex]\sin ^2(u)[/tex]
