law of cosines…caution

Hello everyone! I missed posting yesterday, but it was for a good reason. I was giving out my first #mathsaverfavor! It was for a college stats student, and I will post the problem and explanation this Friday.


For today I decided to show why you should use caution when starting a law of cosines problem. I always tell my students to solve for the largest angle FIRST (using the law of cosines) when it’s an SSS triangle. That is because they ALWAYS like to switch over to the law of sines to find the second angle…which is fine! But if they haven’t planned ahead by finding the largest angle first, then the law of sines is not going to give them the correct answer if the second angle happens to be obtuse!!

So avoid all potential problems in SSS triangles by finding the largest angle first. I think that’s pretty easy to remember, and it will save you a lot of headaches down the road 🙂



My regular Precalc students are moving right along with double and half-angle trig identities. I’ve worked through two common problems using those identities in this video…



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