Friday, January 15, 2010

Geometry: 7-4 (Friday)


Read 7-4 – Now we can find every part of any right triangle, but the ratios are extremely difficult to memorize! Sine = Opposite/Hypotenuse, Cosine = Adjacent/Hypotenuse, Tangent = Opposite/Adjacent. Look at the Key Concept and Example 1 until you get the basic idea, and then write SOH-CAH-TOA or some other reminder in your notes. Say it to yourself a few times to start memorizing it. You'll use this one a lot.

As the sun creeps into the cellar entrance, Sally wakes up and goes wandering through town. She comes across an alchemist, and likes the look of their sign. The “A” is a right triangle 16 inches high and 4 inches wide. What is the measure of the angle at the top? What is the length of the hypotenuse?

In 7-4, work problems 6-16 even, 17, 32-46 even, 49-52 ALL, 70-82 even.

Extra Credit: # 59-61 all, 66, and the following:

Refer to #59. A second is a very small angle measurement equal to 1/60th of a minute, which is equal to 1/60th of a degree. A parsec is a parallax second, in other words the distance from Earth an object would have to be to have a stellar parallax of 1 second, or 1/(60*60) = 1/3600 degree. How many astronomical units are there in a parsec? If NASA scientists find alien life 197 parsecs away on Betelgeuse, how many astronomical units is that?

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