

Wednesday, March 08, 2006

Hi i am zaenab

scribe for today. The 1 class in precal started by Mr.K giving us a word problem on the bored and with it came some questions as usual.

igh tide at the port of montrial occurs at noon today, the depth of the water will be 15m, at low tide. The depth will be 6m, low tide will occurat 6:12 pm.

a) Sketh the graph for this function.
b) Write 2 different equations for this graph. One sine and one cosine.
c) The best time to go fishing off the pier is at 5:18 pm. How deep will the water be?
d) A ship needs a minimum depth of 12m to get into port. What is the maximum amount of time the ship can safely stay in the port?


a)graph @ the bottom (soory i couldn't leave it at the top)

b) sin cos d(t)=-4.5sin[2 pi/12.4(t-3.1)]+10.5

A=-4.5 A=4.5 d(t)=4.5cos[2pi/12.4(t)]=10.5

B=2pie/12.4 B=2pie/12.4

C=3.1 C=0

D=10.5 D=10.5

We get A 15-10.5=4.5 for sin it is negative because the graph goes down and it should go up.

We get B 2pie/B B=12.4 the period which is shown on the graph.

we get c by looking at the graph therfore we see the graph first starts at 0 that is for cosine for sine the graph starts at 3.1.

We all can find D it must be an easy mark for all of us. D is looking at the period and seeing where the sinasoidal axis is in the middle in this case it is 10.5.

c) We are aske how deep will the water be at 5:18 pm and :18 is 1/4 of an hour (i think sorry if i am wrong and please tell me the writr answer) So we convert :18 to hours and that is 0.3. We did that by 18/60=0.3

We will just substitute the new t 5.3 to any of the equations.

We used the second one


than 12-10.5=1.5


1.5/4.5= cos [2pi/12.4(t)]



d)the answer will be in Quad 1 or 4 because cos is positive.

In period 4 we thought we were going to do a pre test but we did a Quiz some people were strugling with the 2 question but than when mr k explained it it became clear. The first question was clear and easy i hope every body got the two marks it was wirth.=)

1) Given the gragh of f(x), sketch the graph of f(x+1)+3.

this is telling us to go 1unit to the left and 3 units to the left.

The graph for #2 is in blue and red.

2)iven the graph of f(x)and g(x):(4marks)

(a) Express f(x) as a function of g(x)

answer; f(x)=g(2x)

(b) express g(x)as a function of f(x)

answer: g(x)=f(x/2)

3) Given the graph of f(x), sketch the graph of f-19X0on the same cartesian plane.(2marks)(The graph will be colored in red look for it at the bottom)

4) State whether of the following is even, odd or nither.(4 marks)

a)f(x)=3x2 Even

b)f(x)=-sin(x) odd

c)f(x)=3x Even

d)f(x)=-4x2+3x Neither

you could check your answer by the following equation.



Jacky is the next sckribe=)
have fun jacky



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