A simple checking mechanism for any geometry problem is to estimate the length of a side or the size of an angle before you begin to calculate.

# Angle (scroll down for triangles)

Estimate the angle shown. Change the slider to include angles up to 360 degrees.

# Sides and Angle on a Right Angled Triangle

On this applet just one side or one angle is measured. There isn’t enough information to calculate the side/angle requested. Estimate the side by comparing it to the given side. Aim for less than 10% or 5% error!