## Saturday, February 17, 2018

### Teaching Geometry - Law of Sines #VNPS

I am sharing this after we have finished the unit.  I need to get the pictures off my phone to make way for vacation pictures!

I taught 1 day of Law of Sines with the ambiguous case.
Next day, Law of Cosines and bearings.
Following day did a mini quiz on Geo Mean, Pythag, Special Rt Triangles, and Right Triangle Trig - just to check in.  Used it as a formative assessment.  Then, practiced some applications of Law of Sines and Cosines.

Law of Sines lends itself well to working at the whiteboards to discover it using right triangle trig.

I gave them this triangle because I didn't want to take the time to describe it in order to draw it correctly:  Board Triangle

Then, I asked them to write the sine of A, resolve for h.
Write the sine of B, resolve for h.
Oh, they both equal h, so set them equal to each other.
Then, rearrange so like variables are on the same side.  Voila, Law of Sines:

Next, added the ratio for C and tried a problem.  These students are really good at solving proportions, so it went smoothly.

We also discovered the Area of a Triangle formula using sin and practiced with that.

Law of Sines Lesson PPT
Law of Sines Board Problems