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# Help watch

1. Hello there,

Could someone please explain this to me, I really don't understand it..
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2. (Original post by User23)
Hello there,

Could someone please explain this to me, I really don't understand it..
Pythagoras Theorem
3. (Original post by TeeEm)
Pythagoras Theorem
I know but how do you find the diameter from that? :/
4. (Original post by User23)
I know but how do you find the diameter from that? :/
What have you tried so far?
5. (Original post by User23)
I know but how do you find the diameter from that? :/
clue: find the length of LB
6. (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
7. (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?
8. (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 )
9. (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 would have done here, 'innit?

Edit: Just saw your edit, ignore this.
10. (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 )
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 :/
11. (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?
12. (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
13. (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.
14. (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
15. (Original post by User23)
Yeah but that'll give me the length of LM
you sure the trig function is correct?
16. (Original post by shawn_o1)
you sure the trig function is correct?
17. I do not think some of the helpers can see how you are meant to do this question

this is just a quick application of Pythagoras theorem
18. (Original post by User23)
I've used both the trig and non-trig methods: no
19. (Original post by TeeEm)
I do not think some of the helpers can see how you are meant to do this question

this is just a quick application of Pythagoras theorem
Yess thank you this has helped, I got an answer of 26cm !
20. you've got to be kidding me... re-read the question properly.

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