Great Circles!( 40 N , 70 W )

Use the points:

CD( 40 N , 150 W )E( 70 N , 150 W )F( 70 N , 70 W )

to find the distance from C to E along a great circle.

( Hint: You will need to find the lengths of the Trapezium CDEF)

Any Contribution and Help will be Appreciated.

Thanks!!!