This worksheet is designed to replace a lecture on using the law of cosines to solve for an unknown side of a triangle. At the start, it has a highlighted "reference information" section which provides the students a summary of all the different approaches for solving triangles, starting with the interior angles theorem. I have found that having these highlighted (in gray) reference sections very helpful for students to study.
I start out class with a 15-minute "mini-lesson," giving my students some basic examples of what today's lesson will be about. I put up a triangle with the basic "SAS" configuration: two known sides and a known included angle, and I show them how to determine the missing side.
Inevitably, students misapply the order of operations when evaluating expressions such as:
100 - 20 cos73
80 cos 73,
which is incorrect. You will need to call this to their attention.
I recommend that my students use their graphing calculators to do all of the "heavy lifting" for them, and simply have them type in the expression 100-20*cos(73) into their calculators, so that they get a more accurate answer with less work, but even so, students will still make this order of operations error.
This worksheet specifically addresses this issue (in problem 4), to have the students analyze the work of others, and to self-check their work.
Once the mini-lesson is over, I have them get to work within their groups on this worksheet.
I use this activity within cooperative groups, and I circulate to make sure they are getting the purpose of the questions.
The file includes spiral review problems.
This worksheet is intended to be written on directly.
Please download the pdf preview file first, so you can see exactly what's included; the product file is a word document, which you may personalize for your students.
Immediately before this worksheet, I use the worksheet named 'Law of Sines Spring 2014' (http://www.teacherspayteachers.com/Product/Law-of-Sines-Spring-2014-1267660
), and immediately after this worksheet, I use the worksheet named 'Law of Cosines Solving for Angles Spring 2014' (http://www.teacherspayteachers.com/Product/Law-of-Cosines-Solving-for-Angles-Spring-2014-1267683