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Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

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Hello there,

Could someone please explain this to me, I really don't understand it..
this question doe.PNG29.0KB

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Reply 1
Avatar for TeeEm
TeeEm
19
Original post by User23
Hello there,

Could someone please explain this to me, I really don't understand it..


Pythagoras Theorem
Reply 2
Avatar for User23
User23
OP
3
Original post by TeeEm
Pythagoras Theorem


I know but how do you find the diameter from that? :/
Reply 3
Avatar for Zacken
Zacken
22
Original post by User23
I know but how do you find the diameter from that? :/


What have you tried so far?
Original post by User23
I know but how do you find the diameter from that? :/


clue: find the length of LB
Reply 5
Avatar for TeeEm
TeeEm
19
Original post by User23
I know but how do you find the diameter from that? :/


How do I find it?

with ease ...

Now try yourself to see how to apply Pythagoras Theorem to find the diameter too.

Start by posting some evidence of work on your part
Reply 6
Avatar for User23
User23
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3
Original post by Zacken
What have you tried so far?


So I found out the length of LB which gives me 21.63330.. but I don't know what to do from here?
Original post by User23
So I found out the length of LB which gives me 21.63330.. but I don't know what to do from here?


Use trig to find angle MLB, then use circle theorem and more trig to get the diameter. Voila!

(That said, sides LM and MB were enough to get angle MLB anyway :biggrin:)
(edited 8 years ago)
Reply 8
Avatar for Zacken
Zacken
22
Original post by shawn_o1
Use trig to find angle MLB, then use circle theorem and more trig to get the diameter. Voila!


You didn't need to find the length LB to find the angle MLB though - a direct application of tan⁡θ\tan \theta would have done here, 'innit?

Edit: Just saw your edit, ignore this. :tongue:
(edited 8 years ago)
Reply 9
Avatar for User23
User23
OP
3
Original post by shawn_o1
Use trig to find angle MLB, then use circle theorem and more trig to get the diameter. Voila!

(That said, sides LM and MB were enough to get angle MLB anyway :biggrin:)


Ok so I found angle MLB to be 33.6900 degrees. then because I've got a right angle I did 90 + that and minused this result by 180 to get 56.30996 degrees for angle LBM. I dont know what to do :/
Original post by User23
Ok so I found angle MLB to be 33.6900 degrees. then because I've got a right angle I did 90 + that and minused this result by 180 to get 56.30996 degrees for angle LBM. I dont know what to do :/


You know how sin, cos, tan work on right-angled triangles?
Reply 11
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User23
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3
Original post by shawn_o1
You know how sin, cos, tan work on right-angled triangles?


Yeah I do but I've got all the lengths I need.. except for the diameter
Original post by User23
Yeah I do but I've got all the lengths I need.. except for the diameter


since you know from the circle theorem that the triangle involving the diameter and LB is right-angled, you only need angle MLB, length of LB and the correct trig function to get the diameter.
Reply 13
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User23
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3
Original post by shawn_o1
since you know from the circle theorem that the triangle involving the diameter and LB is right-angled, you only need angle MLB, length of LB and the correct trig function to get the diameter.


Yeah but that'll give me the length of LM
Original post by User23
Yeah but that'll give me the length of LM


you sure the trig function is correct?
Reply 15
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User23
OP
3
Original post by shawn_o1
you sure the trig function is correct?


is the answer 30?
Reply 16
Avatar for TeeEm
TeeEm
19
I do not think some of the helpers can see how you are meant to do this question

look at this link Q83 in this link
http://madasmaths.com/archive/maths_booklets/basic_topics/various/geometric_mensuration.pdf

this is just a quick application of Pythagoras theorem
Original post by User23
is the answer 30?


I've used both the trig and non-trig methods: no :no:
Reply 18
Avatar for User23
User23
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Original post by TeeEm
I do not think some of the helpers can see how you are meant to do this question

look at this link Q83 in this link
http://madasmaths.com/archive/maths_booklets/basic_topics/various/geometric_mensuration.pdf

this is just a quick application of Pythagoras theorem


Yess thank you this has helped, I got an answer of 26cm !
you've got to be kidding me... re-read the question properly.

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