I am looking for horizontal distance between 2 points. My slope distance is 153.97' and a vertical distance of 91degrees 32minutes 45seconds.

2 answers

what is slope distance*cosineAngle?

This is a very odd vertical angle.
Are you measuring the vertical angle (from the horizon) where 90 degrees is vertically up,
or the zenith angle (from zenith, vertically up) where 91 degrees is just below the horizon?

A vertical angle of 91 degrees requires a special eye-piece/prism, and is past the vertical.

You may want to check the measurements.