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