Possible Clues:

• There are four in a square
• Figures formed by the intersection of two lines
• 12 parts of a dodecagon
• Trig topics
• They may be obtuse, but they also may be right
• Protractors measure them
• In the past, Germans who overcame England's corners
• Protractor's measures
• The viewpoints of some of our ancestors
• Pool shot considerations