Question

What is the approximate distance between Portland, Oregon

(45° north, 122° west), and San Francisco, California (37° north, 122° west). Use 3,960 miles for the radius of Earth.

Answer 1

5669.71 km

Working
The two cities are located on the same longitude.
The formula for the distance then is;
Distance =
`(∅)/(360)`*2*π*3960
where ∅ is the latitude difference-add the latitudes as they are on different sides.
Distance =
`(82)/(360)`*2*
`(22)/(7)`*3960
=5669.71 km