Geometry – How to Find the Measure of an Angle

geometrytrianglestrigonometry

Let ABC a triangle with the measure of angle B equal to 56 degrees and the measure of angle C equal to 36 degrees. P is a point on the side AB, and Q on the side AC so
BP = CQ = 1. Let M be the middle of the side BC and BM = MC = 5. Also, be N the middle of the PQ side. Find out the BMN angle measurement.

Given that there are given lengths of sides, I try to use the sine theorem in the triangles BPM, respectively CQM. Then I used the formula sin(a) + sin(b) = 2sin((a+b)/2)cos((a-b)/2) hoping to get some measure of that angle. Can you give me a hint, please?

Best Answer

You can make the following.

By the law of sines get $AB$ and $AQ$, which gives $AP$ and $AQ$ and by the law of cosines get $PQ$ and $PN$.

Now, by law of cosines get $\measuredangle APQ$ and from this get $\measuredangle BPN.$

Also, by law of cosines get $BN$, by law of cosines again get $\measuredangle BPN$, which gives $\measuredangle NBM.$

Now, in $\Delta NBM$ we have now: $BM$, $BN$ and $\measuredangle NBM.$

Can you end it now?