Tuesday, February 5, 2008

Degrees to Radians

Today, Mr. K firstly stated that we could do somethings to help enhance our blog such as downloading smartboard software to make our blog better by easily retrieving useful images such a slides from class. We can also view the class slides via pdf files on slideshow via download. Anyways, back to the class

He started talking about converting degree's and radians and how to grasp the concept. He first showed us an equilateral triangle, in slide 3, and how all it's angles were of 60° . He then displayed the concept of pressing down on the triangle, forcing one of the angles to be a little less than 60 degrees. That is practically a Radian. A radian is around 57°.

He then showed us an equation that you can view in the slides. The equation was D/180° = R/Pi where D is an angle in degrees and R is an angle in Radians.

In most cases, If D or R is known, one or the other variables can be found via cross multiplying.

In the slide 5, you will find that we converted 25° into Radians. Found after cross multiplying or taking the long method of balancing both sides until one variable is isolated, we will find that 25° is 5pi/36° Radian.

Note that when you do the equation (25°/180° = theta/pi) and you don't indicate the degree units, the 180 will be seen as 180 RADIANS. So it is important to show the units.

On the slide thereafter, we solved the conversion of pi/5 radians into degrees. As we already know that when you divide a fraction by a fraction, you can automatically take a shortcut (view slide 8) from pi/5 * 1/5(Fractions flip when you multiply them) and after you balance it, it'll become 1(180
°)/5 which will equal 36°

After, he went on to a question about a bicycle wheel, but he started explaining the term 'subtend' when some of us forgot what it meant.

So he drew a circle as you see in the slides, and he wrote down θ/2pi = L/2pir where L is the Arc Length. Which can be compared to θ/360°.

He then explained how it works. "An angle compared to the full circle is proportional to a piece of the circle" and "The area of the piece compared to the area of the full circle has the same proportionality."

The bell rang, and he continued the lecture, but then Mr. K started to lose his Smartboard Jedi powers. I'm sure he'll finish the lecture tomorrow.

Well other than that... I forgot what I was gonna say.

Ah Yes, our homework is exercise ONE. Have fun folks :)

P.S. I Love You... I heard that was a bad movie, actually, To the point. Next scribe is.. *no drum roll please) Benofschool A.K.A. Ben.

2 comments:

benofschool said...

Curse you Buzz Lightyear that was unexpected... fine i'll do it

Lani said...

Hi Rence,

The first scribe post of the semester and you are on your way! Nicely done!

Lani