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Welcome to the grade 12 precalculus math blog of St.James Collegiate....

Thursday, April 28, 2011

for the unit test (Exponents and logarithms)

Today I will write about review that we should remember from EXPONENTS & LOGARITHMS.


1. You need to know the Y=2^x,.Y=2^-x, and Y=log2^X(X=2^Y) graphes
and how this things are effect to the graphes
Ex) differents between Y=3^X(narrow) and Y=2^X(wide)
differents between Y=-2^X(the graph looked like flip over the Y=2^X) and Y=2^X
differents between Y=2^(x-1) and Y=2^x-1
differents between Y=log2^x and Y=2^x this is inverse releation

X Y X Y
1 0 0 1
2 1 1 2
4 2 2 4
1/2 -1 -1 1/2
1/4 -2 -2 1/4

2.Logarithmic Function
Y=log2X = X=2^y

Ex) 4=log5625 = 625=5^4

3. know the formulas
loga(MN)=logaM=logaN
loga(M/N)=logaM-logaN
loga(M^n)=nlogaM
logaM=logbM/logba
when the base is 10, we can use our calculator to evaluate!

4. Logarithm
ln=log(e)
ln(e)=1

5. Applications of the exponential function
compound interest
A=P(1+r/n)^nt

where: P=principal amount (amount invested, or what you start out with)
r=rate of interest (always change to a decimal when substituting into the equation)
n=the number of times/year interest is to be calculated
t=the time in Years

Continuous Compound Interest
A=Pe^rt

Where: A=final amount
P=principal amount (amount invested, or what you start out with)
r=rate of interest (always change to a decimal when substituting into the equation!)
t=the time
e=2.718......


Continuous Growth or Decay
A=A0e^kt = A=Pe^rt

Check this out! Logarithmics of Earthquakes....

http://prezi.com/aap4disfexso/logarithmics-of-earthquakes/

What is this all about? What does this have to do with grade 12 precalculus? Please leave a comment.

Wednesday, April 27, 2011

Natural Logarithms

In Monday’s lesson, we learned about Natural Logarithmic Functions…

Natural Logarithm
ic Functions are relatively similar to the Logarithmic Functions we have already learned so far in the unit, the only difference would be the use of an irrational constant known as e.

Like pi, the constant e is a never ending value, therefore is only approximated by the numbers 2.7182…

This value of e is often used as the base of a Logarithmic function in order to find values for matters such as exponential growth/decay and compound interest.

Since a Natural Logarithmic Function has e as its base, the only change we see from what we already know about Logarithmic Functions would be:

Since mathematicians are lazy efficient, the Natural Logarithmic Function above can be simply written as:

The rules we learned about Logarithmic Functions so far all apply to the Natural Logarithmic Functions as well.

That means compressing the following Natural Logarithmic Function:

Would result in the following:

The same can be done for expanding, solving, and verifying...

Graphing and ...

Again, this would be similar to what we have already done. The graphs would look as the graphs of and would, but will be a bit more horizontally compressed due to the added decimals of its approximate value 2.7182...

Other Stuff:

With the help of a calculator we can verify the following the equations below are true:

and

Examples:














Oh, y
eah... here's a picture of a cat doing math!