Presentation on theme: "MM4A6c: Apply the law of sines and the law of cosines."— Presentation transcript:
1MM4A6c: Apply the law of sines and the law of cosines.
2Essential Question:How do I solve problems using the Law of Cosines?
3Law of CosinesTo find the length of a missing side of a triangle, add the sum of the squares of the other 2 sides and subtract twice the product of the other 2 sides and the cosine of the included angle.
5Rules… Must have SSS or SAS information The side that begins the formula will be the same as the angle that ends the formula.Always find the largest angle of the triangle first using the Law of Cosines, then use the Law of Sines to complete the problem if possible.
6Rules continued…REMEMBER: when looking for an angle measure, you take the INVERSE of the value.If you get an error message, and you have rechecked your work, the answer is DNE. The reason for that is sometimes the given information cannot form a real triangle.
9Example 3c=5.1, B=81°, a=4.7Solve the triangle using the Law of Cosines and the Law of Sines
10Example 4Using info given from Example 2, solve the triangle: a=11.3, b=7.2, c=14.8, A=48°HINT: always use the Law of Cosines to find the largest angle first, then use the Law of Sines to solve the triangle.
11Homework/Class work Page 899 9-24 all When possible, start with the biggest angle or side length
12Do NowSolve the triangle: c=7.1, B=29°, a=10 *Use the Law of Cosines to create a ratio, THEN use the Law of Sines to solve*