CK12 - Trigonometry

We can use the figureaboveto determinevaluesof the trig functionsfor the quadrantalangles.For example,

sin(90o) =y= 1.

Example5:use the unit circleaboveto find eachvalue:

a. cos 90o b. cot 180o c. sec 0o

Solution:

a. cos 90
o
= 0

The orderedpair for this angleis (0,1).The cosinevalueis thexcoordinate,0.

b. cot 180ois undefined

The orderedpair for this angleis (-1,0).The ratio is , whichis undefined.

c. sec 0o= 1

The orderedpair for this angleis (1, 0). The ratio is.

Thereare severalimportantanglesin the unit circlethat you will workwith extensivelyin your studyof

trigonometry: 30 o, 45o, and 60o. To find the valuesof the trigonometricfunctionsof theseangles,we need

to knowthe orderedpairs.Let’s beginwith 30o.