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Vector

1401700841083.jpg

If I want to find angle ADC,
I need vector DC and vector DA.


Instead of using those two vector , can I use vector OC and vector BA?
Why cant I obtain the same answer for angle ?
Posted from TSR Mobile
(edited 9 years ago)
Reply 1
Avatar for ztibor
ztibor
10
Original post by Lamalam
1401700841083.jpg

If I want to find angle ADC,
I need vector DC and vector DA.


Instead of using those two vector , can I use vector OC and vector BA?
Why cant I obtain the same answer for angle ?
Posted from TSR Mobile


You may use OC=2*DC ans AB=2*DB vectors to calculate the angle
and you have to obtain same angle as with vectors DC and DB.

If the answer is different then your calculation or method is wrong.
Reply 2
Avatar for Lamalam
Lamalam
OP
3
Original post by ztibor
You may use OC=2*DC ans AB=2*DB vectors to calculate the angle
and you have to obtain same angle as with vectors DC and DB.

If the answer is different then your calculation or method is wrong.


why must I divide the vectors by two? the two sets of vectors both have the same angle?!:confused:
Reply 3
Avatar for davros
davros
16
Original post by Lamalam
1401700841083.jpg

If I want to find angle ADC,
I need vector DC and vector DA.


Instead of using those two vector , can I use vector OC and vector BA?
Why cant I obtain the same answer for angle ?
Posted from TSR Mobile


Your method should give angle ODB, which, on the assumption of symmetry of the figure, should be same as the top angle.

Do you have some actual calculations which give a different value?
Reply 4
Avatar for ztibor
ztibor
10
Original post by Lamalam
why must I divide the vectors by two? the two sets of vectors both have the same angle?!:confused:


You need not divide by 2

I just wrote that (OC, AB) set is the same as (DC,DB)*2 so the angle is the same, too
Reply 5
Avatar for Lamalam
Lamalam
OP
3
Original post by davros
Your method should give angle ODB, which, on the assumption of symmetry of the figure, should be same as the top angle.

Do you have some actual calculations which give a different value?


Why my method gives ODB instead of the actual angle? Is it related to direction of vector?Sorry this q seems a bit silly but I really want to ckear my concept!

Posted from TSR Mobile
Reply 6
Avatar for davros
davros
16
Original post by Lamalam
Why my method gives ODB instead of the actual angle? Is it related to direction of vector?Sorry this q seems a bit silly but I really want to ckear my concept!

Posted from TSR Mobile


Because if you look at the diagram you've drawn, OC and BA meet at D, forming the angle at the bottom
Reply 7
Avatar for Lamalam
Lamalam
OP
3
Original post by davros
Because if you look at the diagram you've drawn, OC and BA meet at D, forming the angle at the bottom


haha yes ! thanks :biggrin:

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