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Saturday, February 22, 2014

I/D1: Unit N - How do SRT and UC relate?

Inquiry Activity Summary
1. The "30" degree triangle at first has the shortest leg labeled "x", the longer leg labeled "x radical 3", and the hypotenuse labeled as 2x. To simplify the three sides of this triangle so that the hypotenuse=1, I divided all the sides by two. I would then have, in order from shortest to longest side: x/2, (x radical 3)/2, and x. Finally, the last step is to label the ordered pairs. Since the triangle is drawn in the 1st quadrant, all values will be positive. The point at the 30 degrees is the origin, which is (0,0). The point at the 90 degrees, or the square angle, is (radical 3 over 2, 0). This is because we go over (radical 3)/2 units for the x value, while the y value stays the same as 0 since we do not go up or down. Lastly, the point at the 60 degrees will be (radical 3 over 2, 1/2). It has the same x value as the previous ordered pair, but since it goes up 1/2 units, that will become our y value.




2. The "45" degree triangle at first has its two congruent legs labeled as "x", while the hypotenuse is labeled as "x radical 2". To simplify the three sides of this triangle so that the hypotenuse=1, I divided all the sides by radical 2 to cancel out the one on the hypotenuse. I would then have, from the two shortest to the hypotenuse: x/(radical 2), x/(radical 2), and x. Since I cannot have a radical on the bottom of the fraction, I rationalize the two legs by multiplying both the top and bottom of the fraction by radical 2. I would then be left with (x radical 2)/2, (x radical 2)/2, and x. Finally, the last step is to label the ordered pairs. Since the triangle is drawn in the 1st quadrant, all values will be positive. The point at the first 45 degrees is the origin, which is (0,0). The point at the 90 degrees, or the square angle, is (radical 2 over 2, 0). This is because we go over (radical 2)/2 units for the x value, while the y value stays the same as 0 since we do not go up or down. Lastly, the point at the second 45 degrees will be (radical 2 over 2, radical 2 over 2). It has the same x value as the previous ordered pair, but since it goes up (radical 2)/2 units, that will become our y value for this ordered pair.



3. The "60" degree triangle at first has the shortest leg (which is now horizontal) labeled x, the longer leg (which is now vertical) labeled as x radical 3, and the hypotenuse labeled as 2x. To simplify the three sides of this triangle so that the hypotenuse=1, I divided all the sides by 2. I would then have, in order from shortest to longest side: x/2, (x radical 3)/2, and x. Finally, the last step is to label the ordered pairs. Since the triangle is drawn in the 1st quadrant, all values will be positive. The point at the 60 degrees is the origin, which is the ordered pair (0,0). The point at the 90 degrees, or the square angle, is (1/2, 0). This is because we go over 1/2 units for the x value, while the y value stays the same as 0 since we do not go up or down. Lastly, the point at the 30 degrees will be (1/2, radical 3 over 2). It has the same x value as the previous ordered pair, but since it goes up (radical 3)/2 units, that will become our y value.





4. The activity helps derive the unit circle by giving us a much better understanding of it as a whole. We can visualize the special right triangles within the unit circle, realizing that their ordered pairs of the hypotenuse and opposite side will create a part of the circle. We will know where the points had come from, along with their corresponding degrees, due to the special right triangles, and we will realize that the unit circle is entirely made up of those triangles and apply that to our previous knowledge about them.

5. The triangles of this activity lie in the first quadrant, where both x and y are positive. However, the positive values of the ordered pairs will change if you draw them in different quadrants--x will be negative in the second quadrant, y will be negative in the fourth quadrant, and both x and y will be negative in the third quadrant. These will apply to the ordered pairs of the triangles. For example, the 45 degree triangle is drawn in the 2nd quadrant. Therefore, the x of its ordered pair will be negative. The 30 degree triangle is drawn in the 3rd quadrant. Both its x and y will be negative in the ordered pair. Finally, the 60 degree triangle is drawn in the 4th quadrant, so only the y value of the ordered pair is negative.


Inquiry Activity Reflection
The coolest thing I learned from this activity was that all of the special right triangles drawn in the first quadrant of a coordinate plane (starting at the origin) and their reference angles drawn in all the other coordinate planes make up the unit circle! All you have to do is connect the points to form a circle. I understood how to unit circle was formed and now it is easier to memorize it as a whole.
This activity will help me in this unit because I now I have a full understanding of where the unit circle comes from. It helps me in memorizing the unit circle and applying it to later concepts, such as 8 and 9. I know how the ordered pairs on the unit circle were derived and their corresponding degrees as well.
Something I never realized before about special right triangles and the unit circle is that they are both connected! I learned that one can derive the unit circle from special right triangles by using the 45 45 90 and 30 60 90 triangles. I like how trigonometry is built on concepts we studied in geometry. It was really interesting to see how the special right triangles applied to the unit circle and it helped tremendously in memorizing it for me.

Monday, February 10, 2014

RWA1: Unit M Concepts 4-6: Conic Sections in real life

1. Parabola: the set of all points the same distance from a point, known as the focus, and a line, known as the directrix.


2. Description of a parabola: The formula or equation for a parabola is (x-h)^2=4p(y-k) or (y-k)^2=4p(x-h). On a graph, a parabola resembles something similar to a curve, forming an arch-like shape when graphed, and is symmetrical on both sides of its vertex. One of the key features of a parabola is the vertex. It is defined as the point where the parabola crosses its axis, and can be identified using (h,k) of the equation or finding the point that is on the axis of symmetry that "divides" the parabola. Another key feature of the parabola is the aforementioned axis of symmetry. This is the line that the vertex lies on and is what splits the parabola into two symmetrical sides, each mirroring each other. It is either vertical or horizontal, depending on whether the parabola is going up and down or left and right. As a result, the equation of the axis of symmetry will start with x= or y=.

To continue with, there are many other key features to the parabola that are introduced in this unit. One of them is the focus, which lies on the axis of symmetry along with the vertex. The focus will always be "inside" of the parabola, meaning that the parabola will be opening towards it. The closer it is to the vertex, the "skinnier" the graph will be, and the farther away the focus is from the vertex, the "fatter" the graph will be. Since the focus is relatively closer to the vertex, as seen in the picture, the parabola is more skinny that it is fat. The focus point is "p" units away from the vertex, a number that can be determined by referencing the formula of the parabola. The variable "p" can also determine which way the parabola is opening up to--for example if p is positive, the graph will open up or right, while if p is negative, the graph will open down or left. To refer to the picture below once again, the graph is opening right, which tells us that "p" was a positive number. In addition, the same distance p is from the vertex is counted in the opposite direction to determine the directrix, which is a line that is perpendicular to the axis of symmetry.

https://people.richland.edu/james/lecture/m116/conics/translate.html


3. Real World Application: A real world application for the parabola can be seen in the headlights of many automobiles, which are in the shape of paraboloids and help focus light into a certain beam. In other words, the shape of the headlights is concave, allowing more light to be beamed from it. This is because the light is directed to the focus of the parabolic mirror as it travels, then is immediately reflected in straight lines that are parallel to the axis of symmetry. The headlight has a smooth inner surface of a glass reflector, which in turn has a layer of bright aluminum. This part of the object serves as a powerful reflector. As a result, this is what makes the beam of headlights and similar objects to be incredibly strong, projecting light with a wider distance and range. It gives off an intense concentrated beam of light.

The light is also beamed in many directions to encourage safer night driving. Therefore, designers do not want all of the light beams to be parallel to the axis of symmetry--some of the light has to be aimed in different places. To do this, they "offset the filament from the focus and change [the direction of] the beam entirely" (http://www.pleacher.com/mp/mlessons/calculus/appparab.html). The positions that the filaments are in are a major factor in determining the different illumination patters that have been desired. For example, if the filament is directed above the focal point, or the focus, the rays of light will be reflected downward. Similarly, if the filament is directed below the focal point, the rays of light will be reflected upward. And if the filament is positioned behind the focal point, then the rays of light will converge. A video explaining this concept further along with other uses of parabolas in real life is embedded below.

 4. Works Cited:
  • http://www.pleacher.com/mp/mlessons/calculus/appparab.html
  • http://www3.ul.ie/~rynnet/swconics/UP.htm
  • https://people.richland.edu/james/lecture/m116/conics/translate.html