Unit 4A

Trigonometry Part 1

Lesson 1: Trigonometry Review


Although the history of measuring angles in degrees is a bit cloudy, one theory suggests «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mn»360«/mn»«mo»§#176;«/mo»«/mrow»«/mstyle»«/math» is used to represent a full rotation because there are about «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mn»360«/mn»«/mstyle»«/math» days in a year. (Ancient calendars were not as accurate as today’s calendar, and «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mn»360«/mn»«/mstyle»«/math» is a much easier number to work with than «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mn»365«/mn»«mo».«/mo»«mn»24«/mn»«mo»§#8230;«/mo»«/mrow»«/mstyle»«/math».) Based on this theory, the constellations would rotate about «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mn»1«/mn»«mo»§#176;«/mo»«/mrow»«/mstyle»«/math» every day.

Using degrees to measure angles is probably comfortable because it is familiar, but in calculus, another unit is used to measure angles: the radian. The radian is a unit derived from measurements based on a circle. And, the use of radians leads to more elegant expressions common in calculus and other advanced math.