help me with 11th grade geometry :(

[donkbee]

I'm trying to help my younger brother with his math homework but I can't figure this problem out. I need to figure out what angles a, b, and c are. The numbers in the circle represent the value of the corresponding angles in degrees.

I sure as hell hope that angle a = 110º. If not, I probably should stop trying to help out I have no idea how to figure out what angles b and c are. Please help!

[donkbee]

oh and I guess if it's not obvious, note that the dot in the middle is the centre of the circle :P

[revolvingiris]

http://www.teacherschoice.com.au/Mat...e_trig_AAS.htm

this help?

[donkbee]

i have only angles, no triangle side lengths.

[revolvingiris]

http://www.ultimacalc.com/html/Triangles_1.html

this goes from drawing a triangle to completion of sides and angles. More of use to you?

edit: sorry for not of being more use. I dont have a calc and cant solve sine/cosine in my head. But I'm pretty sure you can draw a line down your ABC unknown triangle ending with two different triangles. Then solve each triangle using the 90 degree line you drew in. Total the triangle has to =180 degrees so having the total angle measurement, plus the two known 90 angles should be all you need...If you need more info give me a little bit and Ill find a calc and draw it out.

[donkbee]

no, i'm not using trig at all in this problem

[revolvingiris]

Well what tools are you using? Because there are many ways this can be done.

[donkbee]

how do you solve for the remaining angles when you don't know what the angles are after you make two 90º triangles? you don't have any side lengths at all so how can you possibly use trig? Are you wanting to draw a line perpendicular to the chord through angle a (which is 110º from what I could figure out)? If you do that, how do you possibly know what your two new angles are?

I haven't done geometry or trig for ~8 years so maybe I'm just not getting it. But you're supposed to able to solve this problem using rules having to do with chords and quadilaterals.

[revolvingiris]

ok cool, give me a few. In a couple donkaments and not being able to use trig makes it harder.

[mcatdog]

Yeah I got 110 degrees for angle A but it seems like not enough information is given to find angles B and C.

If you take that radius and extend it to the other end of the circle, and assume that vertex A is where it meets the circle, like this:



Well then B+D = 90 degrees because it's an inscribed angle that cuts out 180 degrees of the circle, and D = 50 degrees because it cuts out 100 degrees of the circle, and C = 30 degrees because it cuts out the same arc as the other 30 degree angle. So B = 40 degrees and A = 110 degrees.

However there's no reason why A needs to be in that same place, but when you move the location of A around the circle doesn't change the measure of A, but it does change B and C. Given no information about where A is I don't see how you can determine the measures of B and C.

[donkbee]

thanks for taking a look, Mike. I can't believe I spent 45 minutes trying to solve a problem that can't be solved

[donkbee]

Would you (or anyone else) be willing to take a look at another one? This is the last one for today because I'll be on life tilt soon :P



We're solving for angle FEH, angle GEF, and angle EHG.

I'm pretty sure that angle FEH = 48º, but I can't figure out the other two to save my life. I've spent forever on this one too

In case my diagram is bad, line GH = line GF

[a500lbgorilla]

you have lengths. 2 circle radii on one triangle plus the angle between them mean we know that entire triangle, right?

Can you scan the actual problem? Not that your picture isn't lovely.

[revolvingiris]

Use this to find the lenght of the chord mcatdog drew in.
http://www.mathopenref.com/chord.html

[donkbee]

you have lengths. 2 circle radii on one triangle plus the angle between them mean we know that entire triangle, right?

Can you scan the actual problem? Not that your picture isn't lovely.

The first one I was trying to solve is 5. and the second one is 7.

I can't do 10. either omg tilt I have no idea how to figure out what the radius is. AC = 17.32 and angle BAC = 30 degrees ... I think.

haha sigh.

[donkbee]

Use this to find the lenght of the chord mcatdog drew in.
http://www.mathopenref.com/chord.html

you can't assume that you can draw a chord like that because point a isn't necessarily in line with the line already drawn in the probelm. If that makes any sense ...

[mcatdog]

For #7: draw the chord FH and try to find the measures of all the angles inside triangle EHG.

For #10: If angle AED measures 90 degrees then the measure of the arc it cuts out is 180 degrees, so AD is a diameter of the circle.

[donkbee]

For #7 I did draw the chord but now I have no idea what to do. Here's my attempt:



I'm pretty sure I never worked this hard when I was doing grade 11 math

[mcatdog]

a = s because they cut out arcs of the same length.

[donkbee]

WOWWWW I can't believe I didn't figure that out. haha thanks Mike.

[UG]

Mike is a genius ldo.

Are you still teaching or just finish up?


I was in the 99th percentile in math back in the day. When I took my teaching aptitude test, my results screamed, "you should be a math teacher." I understood math and was good at it, but I didn't enjoy it, as I didn't see how it was applicable to life (I know it is, but not applicable for me). I chose history instead, and absolutely *love* it.

[donkbee]

you gotta do what you love! I maybe should be a teacher but I think it would drive me crazy. I tutor only because it's amazing money.

My brother was getting 26% in math with 1 month left in the term. I don't know if it's possible for him to pass but I'm gonna try. It sucks, though, because I think I care more than he does. I've been spending the last 4 hours trying to do these dumb circle problems while he's been out playing golf with my dad lol.

[UG]

If you get a 26% in high school it usually has nothing to do with how smart you are, it's about want-to. He obviously hasn't done his homework, and in math you really get killed because concepts/skills build on one-another.

I have no sympathy for my students that fail my class or others. High school is set up to be a breeze. Jump through some hoops (homework) and you can do shitty on tests and still pass. Total opposite of college, which is why a lot of kids (everywhere) flunk out.

I hope he gets his grade up, but next time I hope he does what he needs to do when he's supposed to do it.

[donkbee]

I agree that high school is a breeze. In some cases, though, when a certain subject is difficult, some people have the motivation necessary to do well and some don't. I think that a few of the people who fail do so not because they don't care but because they don't know how to do better and so they give up.

I think in my brother's case, he discovered he's not good at the concepts in grade 11 math and he did badly. When he tried to ask his teacher for extra help, he still didn't really understand. He continued to score badly on tests, decided he was just bad at math, and subsequently gave up. There was no motivation to get help because the times he did ask for help, it didn't seem to do him any good.

I agree that it's his fault for not doing his homework on a regular basis and for not seeking help more aggressively, but I can kind of understand why someone might give up when things just don't seem to ever make sense. I hope that by helping him for the rest of the term, I can show him that it's possible to do better if you receive the right kind of help. Maybe then he will learn the type of work ethic necessary to pass a course you're bad at.

Or maybe I'll spend 8 hours a week teaching shit I hate and he'll still fail :P

[a500lbgorilla]

If you get a 26% in high school it usually has nothing to do with how smart you are, it's about want-to. He obviously hasn't done his homework, and in math you really get killed because concepts/skills build on one-another.

I have no sympathy for my students that fail my class or others. High school is set up to be a breeze. Jump through some hoops (homework) and you can do shitty on tests and still pass. Total opposite of college, which is why a lot of kids (everywhere) flunk out.

I hope he gets his grade up, but next time I hope he does what he needs to do when he's supposed to do it.

That's lame. Just give them As anyway.

[mcatdog]

Are you still teaching or just finish up?

I absolutely loved the teaching math part of grad school, but the doing my own research part, not so much. They only giving teaching appointments to people who are in the PhD program so now that I dropped out, I'm not teaching anymore .

[UG]

Are you still teaching or just finish up?

I absolutely loved the teaching math part of grad school, but the doing my own research part, not so much. They only giving teaching appointments to people who are in the PhD program so now that I dropped out, I'm not teaching anymore .

That sucks, I hope you're having fun with poker and whatever else you're doing!

[Halv]

I was gonna make a post in this thread saying something like "LOL WIMMENZRDUM" but then I realized I'd spend half the day trying (and potentially failing) to solve these.

Fucking math. I used to like it but then I got stupid.

[UG]

Fucking math. I used to like it but then I got stupid.

That's me to a T. I was figuring up batting averages and ERA by the time I was like 6 or 7. Then they came in and threw all of these letters and angles and ridiculous functions into everything.

[revolvingiris]

Use this to find the lenght of the chord mcatdog drew in.
http://www.mathopenref.com/chord.html

you can't assume that you can draw a chord like that because point a isn't necessarily in line with the line already drawn in the probelm. If that makes any sense ...

I should get an A for trying!

[JKDS]

for the first one, a = 110 cuz opposite angles of cyclic polygons are supplementary.. b+c = 70...and feel there isnt enough info to solve for b and c. i doubt it though, and am gonna face palm when this thread is bumped like tomarrow with the solution. for partial credit, c might be 50 and b might be 20, but cant prove it and just pulled it out of my ass assuming segment ab and c to the radius were ||.

[givememyleg]

protractor?

[kingnat]

I've gotten two B's in math: Freshman Geometry (in HS).. and Differential Equations. Looking back on things... I still think Geometry is shitty, and I'm pretty pissed I didn't manage an A in Diff EQ....

[Ragnar4]

The problem with Geometry, and the reason it puts everyone on life tilt when they are trying to solve this stuff, is that you have to rely on Proofs (Which we ALL hate with a passion) to know the tricks to solving the triangles.Proofs make this stuff lolez, but you have to be willing to pay attention to the proofs, and go back and reference them.