sin-taad rule

Problem
An airplane flew from Davao City whose latitude is 14° N and longitude of 121.5° E on a course of S 30° W and maintaining uniform altitude. At what longitude will the plane cross the equator?
A. 110° 30' East
B. 122° 26' East
C. 113° 33' East
D. 116° 11' East
 

Problem
Solve for the spherical triangle whose parts are a = 73°, b = 62°, and C = 90°.
 

Solution of right spherical triangle
With any two quantities given (three quantities if the right angle is counted), any right spherical triangle can be solved by following the Napier’s rules. The rules are aided with the Napier’s circle. In Napier’s circle, the sides and angle of the triangle are written in consecutive order (not including the right angle), and complimentary angles are taken for quantities opposite the right angle.