
Algebra PreAlgebra and Basic Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
February 2nd, 2012, 07:13 PM  #1 
Newbie Joined: Feb 2012 Posts: 1 Thanks: 0  Easy ways to remember sin and cos functions of unit circle?
I have a quiz tomorrow in trigonometry, and basically you have to fill out all the sin and cosine functions of the unit circle in 5 minutes...Are there any easy ways or tricks to memorize them fast? The quiz we took (Every kid failed in the class so we get to retake it): http://i1165.photobucket.com/albums/q59 ... /quiz2.jpg As you can see i figured out most of all the values but then i ran out of time...the one things that i can't figure out is if its negative or not (well i can figure it out, but it takes to long)...any trick to that? THANKS! 
February 2nd, 2012, 07:42 PM  #2 
Senior Member Joined: Jan 2012 Posts: 131 Thanks: 0  Re: Easy ways to remember sin and cos functions of unit circ Taken from http://tutorial.math.lamar.edu/pdf/AlgebraTrig.pdf There are 5 "basic" angles, 0, Pi/6, Pi/4, Pi/3, Pi/2. The sign of trig function depends on the location, call quadrant, follow the rule CAST. (cos, all, sine, tangent) Example, all cos function in 1st quadrant((3/2)pi to 0pi) are positive; likewise, all tangents in 3rd quadrant are positive, the rest are negative. Last edited by skipjack; October 23rd, 2017 at 02:36 PM. 
February 2nd, 2012, 07:45 PM  #3 
Global Moderator Joined: Nov 2009 From: Northwest Arkansas Posts: 2,766 Thanks: 4  Re: Easy ways to remember sin and cos functions of unit circ
Easy: There are 5 values (+/) on the unit circle. From LEAST TO GREATEST, they are: 0, 1/2, 1/?(2), ?(3)/2, 1 The ZERO AND ONE always go together (i.e if the cosine is zero, then the sine is +/ 1). The 1/2 and √(3)/2 always go together The 1/√(2) is always paired with 1/√(2) cos(theta) = x sine(theta) = y x, y are both positive in quadrant I, both negative in quadrant III, and you should know the other two. So if asked to fill out a unit circle, I would go from left to right, filling in the xvalues (1, ....) there is just one such point, all the way to the left. (√(3)/2, .....) this would be for two points... (1/√(2), .....) (1/2, ....) (0, ....) (1/2, ....) (1/√(2), ....) (√(3)/2, ....) (1, 0) there is just one of this point, too. Then do the same from top to bottom. It's a little hard to describe via text, but you could knock this sucker out in 30 seconds if you just knew how to move from negative to positive of both x, y axis, and the order of these values from largest to smallest. But don't take it from me  I only had the unit circle as the groom's cake at my wedding!!! Last edited by skipjack; October 23rd, 2017 at 02:40 PM. 
October 23rd, 2017, 05:47 AM  #4 
Newbie Joined: Oct 2017 From: Texas Posts: 6 Thanks: 0 
Hey You can learn basic values of sin, cos, tan at angles 0, 30, 45 degrees. To memorise them, visit https://www.teachoo.com/5225/955/Wha...Evaluating/ 
October 23rd, 2017, 05:54 AM  #5 
Senior Member Joined: Feb 2016 From: Australia Posts: 1,643 Thanks: 571 Math Focus: Yet to find out.  

Tags 
circle, cos, easy, functions, remember, sin, unit, ways 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Translation of the unit circle  rolo564  Complex Analysis  3  January 2nd, 2014 10:57 AM 
UNIT CIRCLE HELP  domen.frandolic  Algebra  2  May 17th, 2011 09:24 AM 
Unit circle  johnny  Algebra  2  March 20th, 2011 02:33 PM 
Unit circle question  jordanshaw  Algebra  6  January 12th, 2011 12:01 PM 
Unit circle problem  brunojo  Algebra  0  March 20th, 2009 04:50 PM 