What is the distance from Portugal to Brazil via boat?

Question

For my AP World History map I need to know the distance from Portugal to Brazil if you are traveling by boat.

Answer 1

I take (0 N / 50 W) in Brazil at Amazon river mouth & (37 N / 9 W).

If c is the arc distance, a & b the latitudes and d=difference in long.

cos c = sin a * sin b + cos a * cos b * cos d

= sin 0 * sin 37 + cos 0 * cos 37 * cos 41

= cos 37 * cos 41

= 0.60273787

c = 52.93376414 arc degrees

=  3176 naut. miles

= 3652.43 st. miles

= 5878 km