Cosine Law
The Cosine law is used when we have a side-side-side (SSSTriangle 1.) or when we have a side-angle-side (SAS Triangle 2.). We us the the angle formula with CosC= in the SSS triangle to find the missing angles, while Csquared= formula is used to find a missing side in the SAS triangle. The angle and the side with the same variable will always be opposite of each other
Lets do an SAS example!
In the SAS we have an angle between 2 sides. We want to find the third side so we would use formula #2 (above).
1.Plug in the appropriate measures
2. Solve for x using the calculator
3. Square root this number
4. Don't forget your units
1.Plug in the appropriate measures
2. Solve for x using the calculator
3. Square root this number
4. Don't forget your units
Lets do an SSS example!
In this triangle we have 3 given sides and we want to find angle C. We will use formula 1 for this problem. We will need to use the inverse of Cos to solve.
1.Plug in the appropriate measures
2. Solve for Cos(C using a calculator
3. Use the inverse of Cos to get your final answer
4. Don't forget your units
1.Plug in the appropriate measures
2. Solve for Cos(C using a calculator
3. Use the inverse of Cos to get your final answer
4. Don't forget your units