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AonZ
Group Title
HELP PLEASE!!!
ABCD is a cyclic quadrilateral in which AB=5. BC=6. CD=7. AD=8. show that cos ADC = 13/43
 one year ago
 one year ago
AonZ Group Title
HELP PLEASE!!! ABCD is a cyclic quadrilateral in which AB=5. BC=6. CD=7. AD=8. show that cos ADC = 13/43
 one year ago
 one year ago

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AonZ Group TitleBest ResponseYou've already chosen the best response.0
dw:1367018505450:dw
 one year ago

AonZ Group TitleBest ResponseYou've already chosen the best response.0
@kropot72 @terenzreignz @Mertsj Help pls Btw i know angles D+B = 180
 one year ago

AonZ Group TitleBest ResponseYou've already chosen the best response.0
@hartnn help please!!!
 one year ago

Mertsj Group TitleBest ResponseYou've already chosen the best response.2
There is a formula for this. First let me relabel your picture so you will understand the formula better.
 one year ago

AonZ Group TitleBest ResponseYou've already chosen the best response.0
ok... only formula i know is angle B + D=180 and angle A+C = 180
 one year ago

Mertsj Group TitleBest ResponseYou've already chosen the best response.2
dw:1367022862806:dw
 one year ago

Mertsj Group TitleBest ResponseYou've already chosen the best response.2
\[\cos A=\frac{a^2+d^2b^2c^2}{2(ad+bc)}\]
 one year ago

Mertsj Group TitleBest ResponseYou've already chosen the best response.2
Just plug into the formula.
 one year ago

AonZ Group TitleBest ResponseYou've already chosen the best response.0
yes!!! that actually worked!! Thank you so much
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
did you get how how found cos A ? he just applied cosine rule, twice. once in triangle ABD and then in triangle BCD, also knowing A+C = 180, so cos C = cos A
 one year ago
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