# Thread: grade 11 trig - Fire tower, Fire and evacuation time...

1. Originally Posted by tangledcurls
how did you find the values for angles :

<ftr = 35

<vrt = 25?

otherwise, I am good.

Tks
I am quite sure you can figure out the angles from what janvdl did, but as i said, i didn't use right-triangles, this is how i found them. i drew a pair of coordinate axis at T and R. see the diagram below

2. ## Thank you!

OMG! The fact that "T is NORTHEAST of R" = 45deg escaped me! I guess I better not do anything that requires knowledge of a compass anytime soon....

Thank you guys, I really appreciate the assistance.

Tangled curls

3. Now that I have that piece of info the rest is clear!

Thanks again,
TC

4. Originally Posted by tangledcurls
Now that I have that piece of info the rest is clear!

Thanks again,
TC
It was a very interesting problem.
Glad we could be of assistance.

5. I just heard from my student, apparently the teacher said to skip it because it was impossible to solve! BUT now we know better....LOL!

You guys are awesome!

6. gah! I was thinking along the lines of using sine and cosine rule but I never thought to encase it in a square to work out the angles. Very interesting indeed, thanks for showing me that.

pat on the back jhevon!

7. Hey Jhevon. Good job on this problem. I did it the same way you did, but rounded a little less. Here are my results:

The distance between the fire and the town is: 58.08 km
The time it will take the fire to reach the town is: 7.26 hours

8. Originally Posted by ecMathGeek
Hey Jhevon. Good job on this problem. I did it the same way you did, but rounded a little less. Here are my results:

The distance between the fire and the town is: 58.08 km
The time it will take the fire to reach the town is: 7.26 hours
i still find it amazing how rounding off figures can change the answer so much (i see similar things happen in my chemistry class. same calculations, but different rounding and the answers seem worlds apart). i guess the more figures you use the more accurate the answer

9. Originally Posted by Jhevon
i still find it amazing how rounding off figures can change the answer so much (i see similar things happen in my chemistry class. same calculations, but different rounding and the answers seem worlds apart). i guess the more figures you use the more accurate the answer
You might find the study of significant figures interesting. The reality is, we're often too lazy to relize the impact of the amount of figures we use in our estimations, assuming that they will remain consistant. Functions like $sinx$, $e^x$, and even to an extent $ln(x)$ and $\sqrt x$, are significantly impacted by the number of digets we round off at with $x$.

10. Originally Posted by ecMathGeek
You might find the study of significant figures interesting. The reality is, we're often too lazy to relize the impact of the amount of figures we use in our estimations, assuming that they will remain consistant. Functions like $sinx$, $e^x$, and even to an extent $ln(x)$ and $\sqrt x$, are significantly impacted by the number of digets we round off at with $x$.
yeah, i see what you mean. and now that i think about it, it becomes painfully obvious. with $e^x$ for example. since the funciton grows exponentially, a small change in x results in a relatively huge change in y. so in that case, rounding off the x-values has a significant effect on the value of the function (given by the y-value)

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