A

C

M

5 2

1. sin A

2. cos A

3. tan A

4. If C = 20º, then cos C is equal to:

A. sin 70 B. cos 70 C. tan 70

25

2152 2 21

2121

Skills Check

CCGPS GeometryDay 17 (8-29-13)

UNIT QUESTION: What patterns can I find in right triangles?Standard: MCC9-12.G.SRT.6-8

Today’s Question:How do we use trig ratios to find the missing sides and angles of a triangle?Standard: MCC9-12.G.SRT.6-8

Finding an angle.(Figuring out which ratio to use

and an inverse trig button.)

Ex: 1 Figure out which ratio to use. Find x. Round to the nearest tenth.

20 m

40 m

20tan

40

26.6o

1 20tan

40x

Tan-1 20 / 40 )

Shrink yourself down and stand where the angle is.

Now, figure out which trig ratio you have and set up the problem.

x

Ex: 2 Figure out which ratio to use. Find x. Round to the nearest tenth.

15 m50 m 15

sin50

17.5 o

1 15sin

50x

Sin-1 15 / 50 )

Shrink yourself down and stand where the angle is.

Now, figure out which trig ratio you have and set up the problem.

x

Ex. 3: Find . Round to the nearest degree.

9

17.29

2.17tan

62

1 17.2tan

9

Ex. 4: Find . Round to the nearest degree.

23

7

23

7cos

72

1 7cos

23

Ex. 5: Find . Round to the nearest degree.

400

200

400

200sin

30

1 200sin

400

Finding a side.(Figuring out which ratio to use

and getting to use a trig button.)

Ex: 6 Figure out which ratio to use. Find x. Round to the nearest tenth.

5520 m

x

20

55tanx

m 6.28x

x55tan20tan 20 55 )

Shrink yourself down and stand where the angle is.

Now, figure out which trig ratio you have and set up the problem.

Ex: 7 Find the missing side. Round to the nearest tenth.

72

80 ft

x

x

8072tan

ft 26x

8072tan x

72tan

80x

tan 80 72 = ( ) )Shrink yourself down and stand where the angle is.Now, figure out which trig ratio you have and set up the problem.

Ex: 8 Find the missing side. Round to the nearest tenth.

24

283 mx 283

24sinx

m 1.115x

x24sin283Shrink yourself down and stand where the angle is.

Now, figure out which trig ratio you have and set up the problem.

Ex: 9 Find the missing side. Round to the nearest tenth.

4020 ft x

2040cos

x

ft 3.15x

x40cos20

When we are trying to find a

side we use sin, cos, or tan.

When we are trying to find an angle we use (INVERSE) sin-1, cos-1, or tan-1.