Protractor Lab
Grab the gold handle and swing the ray around the protractor. The measure updates live — and the lab tells you exactly which scale it is reading, so the wrong-scale trap never gets you again.
1 Drag the ray
Drag the gold handle around the semicircle. One ray stays fixed on the 0° line; the moving ray forms your angle.
Challenge
Make an angle of 125°, then press Check.
2 What to notice
Three ideas this lab makes visible.
The scale follows the opening. The fixed ray points left, so the correct scale is the one starting at 0° on the left. Flip the lab in your mind: if the fixed ray pointed right, you would read the other scale.
Acute vs. obtuse is a sanity check. If your angle looks small but the scale says 140°, you are reading the wrong scale.
Landmarks anchor you. Swing through 90° and 180° slowly and watch the readout — those landmarks never move.