I just purchased a Leupold rangefinder that computes the "True Ballistic Range" to a target, based on the angle. It appears to understate the correction necessary. The manual gives an example: 400 yards at an angle of 30 degrees uphill equates to a true ballistic range of 367 yards. I've been taught that the horizontal distance to a target is what matters, and that can be computed as the line-of-sight distance times the cosine of the angle. Using that approach, the horizontal distance is 346 yards. Can someone please point me in a direction to better understand how the distance when shooting at an angle should be computed? Is the Leupold algorithm correct?