1.4 Evaluating Trig
Functions: Exact and Approximate Values
JMerrill, 2009
Exact Recall: 30o-60o-90o Triangles
Example on Board
Trig Values – See page 39
Approximate Values sin 75o ≈ 0.9659
tan 67o ≈ 2.3559
sec 52o ≈ 1.6247
Revolutions & Partial Degrees
A common unit for measuring very large angles is the revolution, a complete circular motion (360o).
A common unit for measuring smaller angles is the degree, of which there are 360 in one revolution. So, ¼ of a revolution is 90o.
Angles are more precisely measured by dividing 1 degree into 60 minutes and 1 minute into 60 seconds. This gives us very precise locations in any space (latitudes and longitudes).
Example: 25 degrees, 20 minutes, 6 seconds is written 25o20’6”
Degrees Con’t To do by hand:
25o20’6” =
You try: 43o28’12”=
Now, let’s look at these same 2 problems and do them on the calculator. You will use the Angle menu (2nd apps).
' "20 6
25 25.33560 3600
o o
' "28 12
43 43.4760 3600
o o
Add/Subtract in DMS 35o21’42” + 7o 5’30” 42o26’72” which changes to
42o27’12”
Converting to DD Convert 17o39’22” to decimal
degrees. Round to the nearest thousandth
17.656o
Evaluate sin (18o10’)
≈ .3118
sec (20.524o) ≈1.149
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