Students will recognize and apply the sine & cosine ratios where applicable.

Why? So you can find distances, as seen in EX 39.

Mastery is 80% or better on 5-minute checks and practice problems.

Let ∆ABC be a right triangle. The since, the cosine, and the tangent of the acute angle A are defined as follows.

ac

bside adjacent to angle A

Sideoppositeangle A

hypotenuse

A

B

C

sin A =Side opposite A

hypotenuse=

a

c

cos A =Side adjacent to A

hypotenuse=

b

c

tan A =Side opposite A

Side adjacent to A=

a

b

When looking for missing lengths & angle measures what is the determining factor in deciding to use Sin, Cos & Tan?

How do you know which on to use?

Students will recognize and apply the sine & cosine ratios where applicable.

Why? So you can find distances, as seen in EX 39.

Mastery is 80% or better on 5-minute checks and practice problems.

Page 477-478 3-21 all

You can use a calculator to approximate the sine, cosine, and the tangent of 74. Make sure that your calculator is in degree mode. The table shows some sample keystroke sequences accepted by most calculators.

Sample keystroke sequences

Sample calculator display Rounded

Approximation

74

74

0.961262695 0.9613

0.275637355 0.2756

3.487414444 3.4874

sinsin

ENTER

74

74

COS

COS

ENTER

74

74

TAN

TAN

ENTER

A trigonometric identity is an equation involving trigonometric ratios that is true for all acute triangles. You are asked to prove the following identities in Exercises 47 and 52.

(sin A)2 + (cos A)2 = 1

tan A = sin A

cos A

b

ca

A

B

C