1. Agenda 1) Bell Work 2) Outcomes 3) Trig Ratio Review
4) Introduction to solving triangles using Trig Ratios
Tablet password: Trig

2. Bell Work 2/21 1) Use Pythagorean Theorem(simplify radicals) A) B)
2) Use properties of special right triangles to solve
3) Find the sine, cosine, and tangent ratios below:

3. Outcomes I will be able to:
1) Use and understand trigonometric ratios in right triangles

4. 9.5 Trig Ratios
***Pretend you are standing at angle A

5. 9.5 Trig Ratios Pneumonic Device:
If you remember the word SOHCAHTOA, you can remember the trig ratios.
SOHCAHTOA stands for:
S = Sine O = Opposite / H = Hypotenuse
C = Cosine A = Adjacent / H = Hypotenuse
T = Tangent O = Opposite / A = Adjacent

6. Examples Sin A = Sin D = Cos A = Cos D = Tan A = Tan D =
How do these ratios
compare?
Are these
triangles similar?
Why/Why not?

7. Examples 2. Find the sine, cosine and tangent of a 45-45-90. Sin A =
Cos A =
Tan A = = 1
What do we know about all right triangles?
They are similar
Note: Since all triangles are similar, you can simplify any problem involving trig ratios of a to the ratios above B C A

8. Examples 3. Find the sine, cosine and tangent of A in a 30-60-90
Sin A =
Cos A =
Tan A =
***All are similar so they will have these same ratios

9. Examples
4) Use a calculator or your chart to find the following to 4 decimal places:
***Note your calculator must be in degree mode
***Your tablet calculator does not work for these. We will download a new one next week
a) sin 56 =
b) cos 84 =
c) tan 16 =
.8290
*Note you must be able to
convert the trig ratio to a
decimal to be able to solve
for pieces in the triangle
later on.
.1045
.2867

10. Examples 5) Will sine and cosine ever be greater than 1? No Why?
Because the legs of a right triangle can never be longer than the hypotenuse. So you are always dividing them by something bigger than what they are.
Will tangent ever be greater than 1?
Yes, because one leg can be greater than the other.

11. Angle of Elevation
Angle of Elevation: When you stand and look up at a point in the distance, the angle that your line of sight makes with a line drawn horizontally
Where is the angle of elevation?
Angle of elevation

12. Examples
1. The angle of elevation from the base to the top of a playground slide is 55º. The slide takes up 10 feet of space horizontally along the ground. Estimate the height and length of the slide.
1) Draw Picture:
2) Determine what piece you have
3) Create trig ratios
Cos 55 =
Tan 55 =
4) Convert trig ratio to
decimal
5) Solve for variable
hyp
opp
adj

13. Examples
2. You are measuring the height of a tower. You stand 154 feet from the base of the tower and measure the angle of elevation from a point on the ground to the top of the tower to be 38º. Estimate the height of the tower.
Which trig ratio do we use?
Tan 38 =
Solve for the variable

14. Examples Picture: What trig ratio do we have? Solve for the variable
3. You stand at the top of a soapbox derby hill and look downwards. The angle of depression is the angle between your line of sight and a line drawn horizontally. The difference between the elevations at the top and bottom of the hill is called the vertical drop. If the vertical drop is 50 feet and the angle of depression is 13º, find the distance d that a soapbox would travel on this hill.
Picture:
What trig ratio do we have?
Solve for the variable