### Friday's class...

Last Friday we started our class by having our second review quiz in preparing for the Test in May. We're given 8 minutes to answer 4 multiple type questions. Then after that Mr. K showed us the rubric for the Prince of Calculand Project. He discuss it to us for a few minutes. After that Mr. K talked about the Editor's Initiative and he asks our thoughts about it.

After all the discussions we had about the project and the Editor's Initiative, Mr. K showed us and taught us how to answer this related problem that we have been working for a few days.

A spotlight at a school dance is fastened to a wall

a. At what

b. At what speed is the tip of her shadow moving?

First in solving in this problem like other kind of problems is drawing a diagram on what is given to you.

Then next is analyze the drawing. In our diagram there are two similar triangles and based on that we could create a relationship between the two.

8b=1.75a+1.75b

Then find the derivative of that,

6.25 db/dt= 1.75da/dt

Since we know da/dt= 0.75 m/s, juss plug it in and we could figure out db/dt and justplug it in.

Then in order to know what speed is the tip of her shadow. We could use this relationship c=a+b and find the derivative of that,

After all the discussions we had about the project and the Editor's Initiative, Mr. K showed us and taught us how to answer this related problem that we have been working for a few days.

A spotlight at a school dance is fastened to a wall

**8 m**above the floor. A girl**1.75 m**tall moves away from the wall at a speed of**0.75 m/s.**a. At what

**rate**is the length of her shadow increasing?b. At what speed is the tip of her shadow moving?

First in solving in this problem like other kind of problems is drawing a diagram on what is given to you.

Then next is analyze the drawing. In our diagram there are two similar triangles and based on that we could create a relationship between the two.

**b**/1.75=**a+b**/**8**(*a+b=c as shown in the diagram*)8b=1.75a+1.75b

**6.25b=1.75a**Then find the derivative of that,

6.25 db/dt= 1.75da/dt

Since we know da/dt= 0.75 m/s, juss plug it in and we could figure out db/dt and justplug it in.

**db/dt=1.75(0.75)/6.25**

**=0.21 m/s**

So the length of the girl's shadow is increasing**0.21 m/s.**Then in order to know what speed is the tip of her shadow. We could use this relationship c=a+b and find the derivative of that,

**dc/dt=da/dt+db/dt**and plug in the values to get**dc/dt**

dc/dt=(0.75)+(0.21)

dc/dt=dc/dt=(0.75)+(0.21)

dc/dt=

**0.96 m/s**

The tip of the girl's shadow is moving**0.96 m/s.**

That's all we did last Friday....The next scribe is Ara..I'm willing to accept any constructive criticism so don't be afraid to leave a comment. Thanks!
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