1. Right Triangle Trigonometry
Trigonometry Basics
Right Triangle Trigonometry

3. Review
The sin function:
sin A =
hypotenuse
opposite A

4. Review
Review
The cosine function.
cos A =
hypotenuse A
adjacent

5. Review
Review
The tangent function.
tan A =
opposite A
adjacent

6. Sine Function Trig Functions and the Calculator
Try each of these on your calculator:
sin 55°
cos10°
tan 87°

7. Inverse Function Inverse Sine Function Using sin-1 (inverse sin):
If = sin θ
then sin-1 (0.7315) = θ
Solve for θ if sin θ =

8. Inverse Cosine Function
Using cos-1 (inverse cosine):
If = cos θ
then cos-1 (0.9272) = θ
Solve for θ if cos θ =

9. Inverse Tangent Function
Using tan-1 (inverse tangent):
If = tan θ
then tan-1 (0.5543) = θ
Solve for θ if tan θ = 28.64

10. Review
Review
These are the only trig functions you will be using in this course.
You need to memorize each one.
Use the memory device: SOH CAH TOA

11. Most Common Application:r y θ x

12. Review
Review
Solve for x:
x = sin 30°
x = cos 45°
x = tan 20°

13. Review
Review
Solve for θ:
= sin θ
= cos θ
= tan θ

14. What if it’s not a right triangle?
Law of Cosines - The square of the magnitude of the resultant vector is equal to the sum of the magnitude of the squares of the two vectors, minus two times the product of the magnitudes of the vectors, multiplied by the cosine of the angle between them.
R2 = A2 + B2 – 2AB cosθ θ

15. What if it’s not a right triangle? - Use the Law of Cosines:
In any triangle ABC, with sides a, b, and c,