A certain jet is capable of a steady 20 degree climb. How much altitude does the jet gain when it moves 1 km through the air?

We have a right triangle where 1km is the hypotenuse, 20 degrees is the angle of elevation, and x is the altitude gain (the side opposite the 20 degree angle)

So we have

sin20 = x / 1km        ...   multiply both sides by 1 km

(1 km) sin20 = about .342 km