
TRIGONOMETRICAL RATIOS  
INTRODUCTION  
We have drawn a set of axes and used the origin as the centre of an auxiliary circle whose radius is equal to one unit. We have drawn a rightangled triangle in the circle, which we will use to define the trigonometrical ratios. By choosing a radius of this length we have made it easier to find, for each trigonometrical ratio of a given angle, a segment whose length is equal to this ratio. This circle whose radius is equal to one unit is called the unit circle. 

AIMS  

Pedro Férez Martínez 
Spanish Ministry of Education. Year 2001  
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