View Full Version : Help with Problem

Miss Mary

09-17-2005, 12:41 PM

Okay...I have gone over this problem a multiple amount of times and I am still a bit confused with how to get it...Can some one help?

http://i15.photobucket.com/albums/a364/Snodutchess/Geo.jpg

Given:

Line Segment AB is perpendicular to Line Segment BC

m<ABO = (2x+y)

m<OBC = (6x+8)

m<AOB = (23y+90)

m<BOC = (4x+4)

Find: m<ABO

tkhunny

09-17-2005, 12:57 PM

I'm a little puzzled by the notation. My impression is that the given information is in degrees, but the constants do not say so. If it is in Radians, what do 4x+4, 6x+8, or 23y+90 mean for potentially acute angles?

Have you yet noted:

Degrees

(2x+y) + (6x+8º) = 90º ==> 8x + y = 82º

(23y+90º) + (4x+4º) = 180º ==> 4x + 23y = 86º

x = 10º and y = 2º, Then you can answer the question.

Radians (Which really doesn't make any sense form the drawing, but I'll do it anyway, just to emphasize the importance of sufficient notation.)

(2x+y) + (6x+8) = pi/2 ==> 8x + y = (pi/2) - 8

(23y+90) + (4x+4) = pi ==> 4x + 23y = pi - 94

x = (7/120)*pi - 1/2 and y = (1/30)*pi - 4

I wonder, if you submitted the "Radians" version on a homeowrk assignment, would it get full credit or would it be marked down for significantly ignoring the drawing.

Miss Mary

09-17-2005, 01:04 PM

I have just started 9th grade Honors Geometry....I have never heard of radians yet..but I am sorry if I didn't state that they were not in degrees..however they are. That is why I M before each angle...it is to signify that the m means measure. I am so confused at the moment so I am sorry if I am coming out with this incorrectly.

The teacher might be impressed with radians, but I don't really know if she will accept it.

stapel

09-17-2005, 03:24 PM

Yes, "m(anglename)" usually represents "the measure of the named angle". That wasn't the question.

The tutor was inquiring after the units on the measure. What you posted was similar to asking "how many tons are in 1400 x's", without saying if you mean English or metric tons, and without saying what unit "x" is. (Pounds? Milligrams? What?)

Units are important.

Eliz.

Miss Mary

09-17-2005, 06:07 PM

Oh sorry...I was a bit confused...I didn't know that there was such a thing as any other way of measuring an angle other than degrees...I never heard of radians...Sorry again.

stapel

09-17-2005, 06:28 PM

You'll hear of radians soon enough. And, if you study in Europe, you may also hear of gradians. My post wasn't meant as a rebuke; it was just FYI. The tutor was asking a valid question.

Now you know. :wink: :D

Eliz.

Miss Mary

09-17-2005, 09:10 PM

Thanks....lol :oops:

Denis

09-18-2005, 12:50 AM

If you want to get a headstart on radians:

http://mathworld.wolfram.com/Radian.html

TchrWill

09-18-2005, 11:39 AM

Just another thought:

"IF" the given expressions were meant to be radians, then in radian terminology, 2x + y + 6x + 8 = Pi/2 radians or 8x + y = Pi/2 -8 radians.

Similarly, 23x + 90 + 4x + 4 = Pi or 23y + 4x = Pi - 94 radians

Solving, y = 2 and x = 10.

2(10) + 2 + 6(10) + 8 = 90º = Pi/2 radians

2(23) + 90 + 4(10) + 4 =180º = Pi radians

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