Hello from MrBillDoesMath!
Answer:
tan ^(-1) (6/7), the last expression in the list
Discussion:
In a right triangle,
tan(@) = side opposite angle\side adjacent to angle.
In our triangle, this becomes
tan(@) = LM \ MN = 6/7 =>
@ is the inverse tangent of (6/7)
Regards,
MrB