- Joined
- Nov 30, 2008
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I have 3 QR questions from DAT Destroyer (2008 editon) that I'd like someone to explain to me if possible.
#72
Evaluate the following: 600e^-x = 300
I get to the part where it's -x=ln(1/2) but the correct answer is x=ln(2/1).
Could someone explain to me why it changes from 1/2 to 2/1?
#81
What is Cos(495 degrees)?
I understand the Quadrant thing where you go around 450 degrees which leaves the angle at 45 degrees.
The answer is -Cos(45 degrees) = -(√2/2)
It says it's a reference angle. Is that something we can figure out or is that something we have to memorize somewhere?
#87
This could be taken from a lot of problems (like #86 even).
6 people are running for 4 positions. How many different combinations can there be?
This is an easy problem. 6x5x4x3 = 360.
The part that I don't get, which almost seems irrelevant, is that in the answer it shows (6x5x4x3x2)/(2) and the 2s just cancel out.
Why do they have those extra "2s" and is there kind of example where they actually are significant?
Thanks!
#72
Evaluate the following: 600e^-x = 300
I get to the part where it's -x=ln(1/2) but the correct answer is x=ln(2/1).
Could someone explain to me why it changes from 1/2 to 2/1?
#81
What is Cos(495 degrees)?
I understand the Quadrant thing where you go around 450 degrees which leaves the angle at 45 degrees.
The answer is -Cos(45 degrees) = -(√2/2)
It says it's a reference angle. Is that something we can figure out or is that something we have to memorize somewhere?
#87
This could be taken from a lot of problems (like #86 even).
6 people are running for 4 positions. How many different combinations can there be?
This is an easy problem. 6x5x4x3 = 360.
The part that I don't get, which almost seems irrelevant, is that in the answer it shows (6x5x4x3x2)/(2) and the 2s just cancel out.
Why do they have those extra "2s" and is there kind of example where they actually are significant?
Thanks!