Trigonometry Challenge

Give it a try!
From a granite post, proceed 195 ft. east, then along a bearing of S32°E for 260 ft., then along a bearing of S68°W for 385 ft, and finally along a line back to the granite post. 

• What is the area of this plot of land?
• If 1 acre = 43,560 ft² and land is taxed at $115 per acre, how much would the taxes be for that plot of land?
• What would the directions (bearing and distance) for traveling the last leg of the trip back to the starting point be?

Bring your answers and work to class on Monday for a chance to earn some extra credit!

Trigonometry Enrichment - Proving the Law of Sines

A Proof of the Law of Sines
     - Presented by khanacademy.org

This Week's Mental Math Moment - Letting Go of the Calculator

Multiplying Two Digit Numbers

Many of us find it relatively easy to multiply by 2, 3, 5, and 10.  If we can express our two-digit numbers as multiples of some of these numbers, then it will make  multiplying them much easier.

Let’s start with a simple example:  12 x 18.  We have all learned our multiplication tables up to 12, so let’s factor  the 18 into 9 x 2. 

Now we have the following:

            12 x 18 = 12 x 9 x 2

                       = 108 x 2

                       = 216

Another example is 24 x 21.  Factoring 24 by 2 and 21 by 3, we can multiply as follows:

           24 x 21 = 12 x 2 x 7 x 3

                      = 12 x 7 x 3 x 2  (Using the Commutative Property)

                      = 84 x 3 x 2

                      = 252 x 2

                      = 504

This takes some practice, but you’ll be amazed by what you can do if you give it a try! 

Chapter 9 Test on Friday

Be sure to study for the Chapter 9 Test this Friday.
Here's a quick summary of the topics covered:

• Solving right triangles with SOH-CAH-TOA
• Solving any triangle using the Law of Sines and the Law of Cosines
• Finding areas of triangles using Heron's Formula, the SAS Area formula, or the AAS/ASA Area formula.  Remember that for this section you will not be permitted to find additional parts of the triangle, so you have to know all three formulas and when to use them.
• Applying trig to Navigation and Surveying
• Use Headings, Bearings, and Compass points to sketch a diagram of the directions given
• Use Trig to find areas of polygonal regions
• Use Trig to find directions back to a starting point

Today's Funny Math

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