Find the perimeter of the spherical triangle.

Assume the radius of the earth to be 3960 miles. Three positions on the surface of the earth are defined by: i) Latitude= O degrees, longitude= 60 degrees ii) Latitude= 90 degrees, Longitude= 60 degrees. iii) latitude= 0 degrees, longitude= 90 degrees. My teacher gave me these hints. 1.) Draw a diagram of a sphere 2.) The coordinates form a right triangle 3.) Use proportions 4.) Use the circumference formula. I would really appreciate your help. Thank you so much.

Here is another hint: two points are on the equator and one point is the north pole, so it is an isosceles triangle with two right angles.

Latitude is theta and longitude is phi of polar coordinate
point 1: x = 0, y = 0 and z = R cos o = R
Point 2: (R*sin 90*cos 60, R*sin 90* sin 60, 0)
Point 3: ( 0, 0, R)
side 12 = sq rt[(R/2)^2 + +(R*sq rt(3)/2)^2 + R ^2] = R* sq rt(2)
side 23 = sq rt[(R/2)^2 + +(R*sq rt(3)/2)^2 + R ^2] = R *sq rt(2)
side 31 : sq rt(R^2) = R
Perimeter [2*sq rt(2)+1]*R = 15161 mile