HONORS GEOMETRY 8.6. Law of Sine/Law of Cosine Day One

Do Now: The top of a signal tower is 250 feet above sea level. The angle of depression from the top of the tower to a passing ship is 19°. How far is the foot of the tower from the ship? Jay is standing 50 feet away from the Eiffel Tower and measures the angle of elevation to the top of the tower as 87.3°. Approximately how tall is the Eiffel Tower?

Do Now: Grab one of each of the packets up front. Do the 1 st problem in both.

Hmmm…. What happens if we do not have a right triangle and we want to find the sides/angles of the triangle? Realize– trigonometry, Pythagorean theorem- they are out the door the minute you don’t have a right angle!

Law of Sines

Example One: Find p. Round to the nearest tenth.

Example Two: Find x. Round to the nearest tenth. 6 x 57 °

Example Three:

You Try! Find c, <c and x. Round to the nearest tenth. 43 x

Depending…. We may not have enough information about the triangle to use law of sines..

Law of Cosines

Example Four: Find x. Round to the nearest tenth. We know two sides AND the included angle = Law of cosines!

Example Five: Find <L.

Your Turn! Find r and <P

Example Six: AIRCRAFT From the diagram of the plane shown, determine the approximate width of each wing. Round to the nearest tenth meter.

Example Seven: Solve Triangle PQR

You Try! Solve Triangle RST

Practice Problems Try some on your own/in small groups As always don’t hesitate to ask me questions if you are confused!

Exit Ticket: Solve triangle ABC