## Monday, March 5, 2007

Hi I'm Albert and I'm your scribe for tonight. Sorry for the late post i just got from work though. Anyways, we started the morning class or it's better to say they started the morning class(because I'm late hehe)talking about Blogging on Blogging or what we most know as "BOB". He praised Mr. Siwwy(or Chris is that right?)for doing a good job on BOB. We reviewed some stuff on previous lessons like reciprocal and inverse functions and so as even and odd functions.

After that, we finished answering the problem that we have last friday. I wonder how can i copy Mr. K's slideshows?any suggestions?

That's not a big deal though I'll just explain it slide by slide and you can just take a look at Mr. K's slideshows as a reference.

Slide 1: We need to answer those questions step by step

Slide 2: Using only the two given which are (Dec 21 at 9:15 am & June 21 at 3:15 am)we used it to graph the sinusoidal function. First, we convert the 15 minutes = 0.25 hour so 9:15 becomes 9.25 and 3:15 becomes 3.25. Those two are going to be your max and min of your function respectively. To get your sinusoidal axis add those two numbers and divide it by 2. Second, we count the days between Dec 21-June 21 which is 182 days. It's up to you where to start your graph but it's more comfortable what Mr. K did. He didn't start his graph from Dec 21, instead he started his graph from Jan. 1 to make it easier. Lastly, take note that 182 days is not the period of the function but only the half of it because distance from max to min is only halfway of the period.

Slide 3: We need to write 2 equations using sine and cosine. Using the DBAC rule or order you can get it without sweat.

Slide 4: Using either of the two equations(sine and cosine)that we did we can predict what time will the sunrise on April 6. Mr. K said that we better used the equation that doesn't have "Phase Shift" so it will be easier to us.

Slide 5: First, we must know how many days of the year will the April 6 come to which is 96 days using the knucke trick as a guide. Plug it back in to your equation and you'll get the answer. The answer is 5.4818 is not the final answer yet. Left 0.4818 and convert it into minutes by multiplying it into 60 and you'll get 28.9129. So the final answer would be 5:29 am.

Slide 6: We are looking now for the average time which means the sinusoidal axis of the graph. In the graph it says 6.25, take out the 0.25 and convert it into minutes so 0.25 x 60=15. Therefore the answer is 6:15 am.

Slide 7: I don't know how will I explain this part but I'll give my best shot. Just like we did in Slide 4 we substitute the days to get the time but for this question u have to do it in reverse. You're going to solve for the input with a given output. Use let (-) = 2pie/364(d+10) to make it easier for you. But then Mr. K said that sometimes it's going to make it more complicated.

Slide 8: After using your calculator, you'll get the ARCCOS(0.25)=1.3181. It is recommended and more accurate if your decimal places will be four units. After that don't forget you still have the let (-) and solve for it. Quadrant I and IV of cosine is positive so the answer would be both positive. So just by taking a look at the Slide 8 you can see how the process and how it was solve and your answers are 66 and 278 days.

Slide 9: In the slideshow, it shows you that 66th day will be at March 7 and so as 278th day will be at October 5.

Slide 10:How many days of the year will the sun rise later than 7 am?
By looking in the graph those days between 66th day and 278th day will be the answer. Therefore 278-66=212 days

Sorry for the very very late post..I'm just not used to post like this so please bear with me. For the question this afternoon, we're not done doing it so If you still want me to do a scribe for it I will do it. See ya guys later! By the way Sandy will be our next scribe..