[tex]\frac{\cos(u)\sec(u)}{\tan(u)}=(\cos (u)\sec (u))\mleft|\frac{1}{\tan (u)}\mright|[/tex]
The first box contains 1/tan(u)
[tex]=(\cos (u)\frac{1}{\cos(u)})|\cot (u)|[/tex]
The second box constains cot(u). Now, simplifying cos(u) we have:
[tex]=|\cot (u)|[/tex]
The last box contains cot(u)
I used "| |" to identify the boxes.
