1. Trigonometric Ratios
Please view this tutorial and answer the follow-up questions on loose leaf to turn in to your teacher.

2. Identifying Parts of a Right Triangle
Hypotenuse – always across from the 90° angle
Side Opposite – always across from the angle being referenced
Side Adjacent- always touching the angle being referenced
*Note that all angles are marked with capitol letters and sides are marked with lower case letters C B
Angle C measures 90°

3. Identifying Parts of a Right Triangle
What side is opposite of angle A?
Side BC
What side is opposite of angle B?
Side AC
What side is adjacent to angle A?
What side is adjacent to angle B?
What side is the hypotenuse?
Side AB A C B

4. Trigonometric Ratios (only apply to right triangles)
Sine (abbreviated sin)
Sin x° =
Example: A C B
Sin A =

5. Trigonometric Ratios (only apply to right triangles)
Cosine (abbreviated cos)
Cos x° =
Example: A C B
Cos A =

6. Trigonometric Ratios (only apply to right triangles)
Tangent (abbreviated tan)
Tan x° =
Example: A C B
Tan A =

7. Helpful Hint to Remember the Trig Ratios
SOH (sine = opposite / hypotenuse)
CAH (cosine = adjacent / hypotenuse)
TOA (tangent = opposite / adjacent)
Remember SOH CAH TOA

8. Time to Practice Identify the following trig ratio values C 3 B
Sin A = Sin B=
Cos A = Cos B=
Tan A = Tan B= 4 5 A

9. Time to Practice Identify the following trig ratio values C 3 B
Sin A = Sin B=
Cos A = Cos B=
Tan A = Tan B= 4 5 A

10. More Practice Identify the following trig ratio values B
Sin A = Sin B=
Cos A = Cos B=
Tan A = Tan B= 13 5 A C 12

11. More Practice Identify the following trig ratio values B
Sin A = Sin B=
Cos A = Cos B=
Tan A = Tan B= 13 5 A C 12

12. How to use the trig ratios to find missing sides
Step 1: Make sure your calculator is in degree mode
Step 2: Label the right triangle with the words opposite, adjacent, and hypotenuse based on the given angle (Note: Do not use the right angle.)
Step 3: From the given information, determine which trig ratio should be used to find the side length
Step 4: Substitute in the given information

13. How to use the trig ratios to find missing sides (continued)
Step 5: Put a 1 under the trig ratio
Step 6: Cross multiply
Step 7: When x=, put problem into your calculator (Note: you may have to divide first to get x by itself)
(NOTE: The angles of a triangle MUST add up to be 180°)

14. Example
Given the following triangle, solve for x.
60°
8 cm x

15. Let’s Talk Through the Steps
Step 1 : Check calculator for degree mode
Press the Mode button and make sure Degree is highlighted as in the picture below

16. Step 2 Label the triangle according to the given angle 60°
8 cm- HYPOTENUSE
X - OPPOSITE

17. Step 3 Identify the trig ratio we should use to solve for x. 60°
8 cm- HYPOTENUSE
From the 60° angle, we know the hypotenuse and need to find the opposite. So we need to use SINE.
X - OPPOSITE

18. Step 4 Substitute in the given information into the equation. 60°
8 cm- HYPOTENUSE
Sin x°=
Sin 60° =
X - OPPOSITE

19. Step 5 Put a 1 under the trig ratio 60° 8 cm- HYPOTENUSE Sin x°=
X - OPPOSITE

20. Step 6
Cross multiply to solve for x
Sin 60° = 1
8 sin (60°) = x

21. Step 7
Since x is already by itself, I can enter the information into the calculator.
Therefore, we can state that x=6.93.

22. Let’s Look at Another Example
Suppose that when we set-up the ratio equation, we have the following:
Tan 20° =

23. What Happens When We Cross Multiply?
Tan 20° = 1
X tan 20° = (How do we get x by itself?)
tan 20° tan 20° (Now we have to divide by tan 20° in order to solve for x)
X = 4
tan 20°
X = 10.99

24. How to use the trig ratios to find missing angles
Step 1: Make sure your calculator is in degree mode (See slide 15)
Step 2: Label the right triangle with the words opposite, adjacent, and hypotenuse based on the given angle (Note: Do not use the right angle.)
Step 3: From the given information, determine which trig ratio should be used to find the side length
Step 4: Substitute in the given information

25. How to use the trig ratios to find missing sides (continued)
Step 5: Solve for x by taking the inverse (opposite operation) of the trig ratio.
Step 6: When x=, put problem into your calculator.

26. Calculator Steps for Finding Angles
To solve for x, remember to take the inverse trig function.
On the calculator, you can find the inverse trig functions by pressing 2nd and then the trig function.

27. Let’s Look at an Example
Given the following triangle, solve for x.
62 cm
90° x
200 cm

28. Step 2 Label the sides opposite, adjacent, or hypotenuse from angle x.
62 cm
90°
200 cm
HYPOTENUSE x

29. Step 3
Since we have the opposite and the hypotenuse, we need to use SINE.
OPPOSITE
62 cm
90°
200 cm
HYPOTENUSE x

30. Step 4 Substitute in the given information into the equation. x
OPPOSITE
62 cm
Sin x =
90°
200 cm
HYPOTENUSE x

31. Step 5
To solve for x, we need to take the inverse of sine on both sides.
OPPOSITE
62 cm
Sin x =
90°
Sin-1 (sin x) = Sin-1
200 cm
HYPOTENUSE x

32. Step 6 Now just type in the x= on your calculator. Sin x =
Sin-1 (sin x) = Sin-1
X = Sin-1
X = 18°

33. Now It’s Your Turn!
Use what you’ve just reviewed to help you answer the following questions.
Submit all of your work to your teacher after completing the tutorial.
Don’t be afraid to go back through the slides if you get stuck.
GOOD LUCK!

34. Problem #1 Complete the following ratios. Sin A = Sin B = 6 cm C A
Cos A= Cos B=
Tan A= Tan B=
6 cm C A
90°
8 cm
10 cm B

35. Problem #2
Solve for x and y.
40 ft
90° y
55° x

36. Problem #3
Solve for angles A and B. A
5 in B
90°
7 in C