skepticality
Member
hi i need help with this question
-
Looking for HSC notes and resources? Check out our Notes & Resources page
Maths Question (1 Viewer)
- Thread starter skepticality
- Start date
P
pLuvia
Guest
For convenience let the angle sign be "^"
......................
In triangle ABC
^ECB = 20*
^FAB = 30*
^BDC = 50+20 = 70* (sum of remote interior angles)
^CED = 70*
^FEB = 110*
.: ^EFC = 130*
^CEF = 180 - (^ECB + ^EFC)
= 180 - (20 + 110)
= 50*
......................
In triangle ABC
^ECB = 20*
^FAB = 30*
^BDC = 50+20 = 70* (sum of remote interior angles)
^CED = 70*
^FEB = 110*
.: ^EFC = 130*
^CEF = 180 - (^ECB + ^EFC)
= 180 - (20 + 110)
= 50*
Last edited by a moderator:
That solution by pLuvia is correct, i'll just add some explanations to help guide you through the answer:
^ECB = 20*
^FAB = 30* [since the base angles must add up to 160 in the isos triangle therefore each angle must add up to 80 as the base angles of an isos triangle are equal]
^BDC = 50+20 = 70* (angle sum of 2 interior angles = opposite exterior angle)
^CED = 70* (angle sum of triangle CED)
^FEB = 110* (supplementaries on straight line)
.: ^EFC = 130* (angle sum of triangle EFC)
^CEF = 180 - (^ECB + ^EFC)
= 180 - (20 + 110)
= 50*
^ECB = 20*
^FAB = 30* [since the base angles must add up to 160 in the isos triangle therefore each angle must add up to 80 as the base angles of an isos triangle are equal]
^BDC = 50+20 = 70* (angle sum of 2 interior angles = opposite exterior angle)
^CED = 70* (angle sum of triangle CED)
^FEB = 110* (supplementaries on straight line)
.: ^EFC = 130* (angle sum of triangle EFC)
^CEF = 180 - (^ECB + ^EFC)
= 180 - (20 + 110)
= 50*
P
pLuvia
Guest
hehe thanks Riviet
I
icycloud
Guest
1. Sorry to spoil the party guys, but ^BDC does not equal 70, it is in fact 100.
2. It follows that ^CED is not 70, it is in fact 40.
3. However, the more fundamental error lies when leaving out ^CEF in saying "^CED and ^FEB are supplementary". That is, ^CED + ^FEB is not equal to 180, the correct equation is ^CED + ^CEF + ^FEB = 180.
4. Thus, the proof is wrong. (Unless I overlooked something really badly, or I somehow have a different diagram to everyone else's...)
2. It follows that ^CED is not 70, it is in fact 40.
3. However, the more fundamental error lies when leaving out ^CEF in saying "^CED and ^FEB are supplementary". That is, ^CED + ^FEB is not equal to 180, the correct equation is ^CED + ^CEF + ^FEB = 180.
4. Thus, the proof is wrong. (Unless I overlooked something really badly, or I somehow have a different diagram to everyone else's...)
Last edited by a moderator:
P
pLuvia
Guest
Yep my bad, I see it I'll fix it up thanks Icycloud
P
pLuvia
Guest
Well that just makes it even harder 
skepticality
Member
i think the question is fucked..
Bookie
Banned
You know whats hilarious Michael?
The fact that you made the subject of thsi thread 'maths question'.
Now being in a mathematics forum, I dont think many people were actually expecting anything mathematics related, but hey, SHAZAM! Maths Question. MMMMMMMmmmmmmmmmmmmmaths. It is also, ingeniously, a question. I want't quite expecting a thesis on Mathematics Extension 1. More interesting is the fact that isis something we had not learnt or did we need to learn for teh test this morning [which I'm hopeful of a 58 for. Fucking height of tower.] Rant finished.
The fact that you made the subject of thsi thread 'maths question'.
Now being in a mathematics forum, I dont think many people were actually expecting anything mathematics related, but hey, SHAZAM! Maths Question. MMMMMMMmmmmmmmmmmmmmaths. It is also, ingeniously, a question. I want't quite expecting a thesis on Mathematics Extension 1. More interesting is the fact that isis something we had not learnt or did we need to learn for teh test this morning [which I'm hopeful of a 58 for. Fucking height of tower.] Rant finished.