Question

Just want to be sure I'm doing this right (Trigonometry and Right Triangles)

Answer 1

please post this in the math section

Answer 2

I hate things that have to do with these kind of calculations.

Answer 3

This is the math section.

Answer 4

Haha....Isn't this the math section, though?

Answer 5

sorry i was thinking wrong my bad

Answer 6

No problem. We all have those moments.

Now, on with how I try to do this. I just want to be sure I have the idea of how to use these ratios correctly.

Answer 7

First, based on reasoning and common sense, I can gather that triangle ABE has these three known sides:

The angle, 45*
The adjacent side, 30 cm.
To solve the question, I need the opposite side, correct?

Answer 8

I'm a bit insecure in my math, so confirmation would be nice. (:

Answer 9

With the angles given and one side, you can calculate every single side in that figure. It's just a tediuous process.

To solve this question you need two things:

1) the opposite side in the ABE triangle : AE (yes, you were correct)

but you also need

2) the side that opposes the 30 degree angle in the BED triangle : ED

since AD = AE + ED.

Answer 10

*tedious, damn you grammar

Answer 11

Yeah, I figured. One step at a time, though, right?

XD

Answer 12

Anyways, I used Tan to solve it. Now, it goes like this, right?

Tan(45=opposite/adjacent (30)

Right?

I'm a tad rusty on this stuff.

Answer 13

Tan(45 is 1, according to my calculator.

Answer 14

Well, you need to use what is best to / is possible to use.

For 1) yes, tan is the answer to it: tan(45) is 1 and tan(45) is also AE/BE.

Which means AE = BE. Which is fairly evident if you ignore trigonometry for 2 seconds and notice the BAE angle is also 45 degrees and your triangle is an isosceles triangle with a 90 degree angle.

Answer 15

But that's the fun of math sometimes - you get plenty of confirmations along the way.

Answer 16

Huh. Good to know.
This feels like the kind of puzzle I would love; the ones that have so many bits you need to put together. But, for the sake of time, I have to ignore half of those...

Answer 17

Back to the prompt.
So, with that information, and using algebra, I figure that the opposite side measure 30 cms. Did I do that right?

Answer 18

Then there's ED - look for it in the BED triangle.

You have the opposite side of the 30 degree angle (BE=30 cm) and you're interested in the side that opposes the 30 degree angle (ED).

It's the same stort, except it's tan(30) now - which (I hate calculators) is 1/2 / sqrt(3) /2 which is 1/ sqrt(3).

So ED/BE = ED /30 cm=1/sqrt(3) which means ED = 30cm / sqrt(3).
Since sqrt(3) is 1.73...blablabla ... damn it, I hate calculators.

Answer 19

Oh yeah, we're past that. AE=BE=30 cm.

Answer 20

Okay. XD. I just used simple algebra, moving bits of he equations over and whatnot.

That just leaves me to solve for triangle BED, so I can get the side, and add it to 30.

Answer 21

Yup, which is what I just did up there.

Answer 22

But, unless I read it wrong, 1.73+30=/=any of the answers.

Answer 23

It has to be 40 something. It's A. I hate calculators.

Answer 24

No no no ... It's 30 / 1.73 + 30.

Answer 25

Hang on, this won;t let me reply with my full post. BRB

Answer 26

Okay, let me try and solve it algebraically.
Tan(30=op/adjacent
Tan(30=op/30
.57=op/30
17.32=op
That's what I got, anyways.

Answer 27

Right, you're spot on.

Answer 28

47.32 is one of the answers, so...Did I do everything right?
(I'm not dealing with sqrt; I haven't heard about it until now.)

Answer 29

I'm an engineering student, I don't give precise answers.

Answer 30

Ah. Well, thank you for your time; you were an amazing help! (:
Merry Christmas!

Answer 31

Yeah, you did. The logic is right.

sqrt stands for square root.

Tangent is defined as sine/cosine. Tan(30) is sin(30) / cos(30). Both sin(30) and cos(30) are well known values ( sin(30) is 1/2, cos(30) is sqrt(3)/2 ). So instead of memorizing or using a calculator, I just do the division between those - to which I get that tan(30)=1/sqrt(3).

Answer 32

Or .57 that you have calculated with a calculator. Whatever, the point is that you are right and it's A.

Answer 33

You've dealt with everything right.