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 one year ago
Help please :) Yr11 3 unit question on trig
In triangle ABC, acosA = bcosB. Prove using the cosine rule, that the triangle is either isosceles or rightangled
 one year ago
Help please :) Yr11 3 unit question on trig In triangle ABC, acosA = bcosB. Prove using the cosine rule, that the triangle is either isosceles or rightangled

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ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2good:) so vat is cosA?

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2Nw if u r to prove that the triangle is isoscles u need to show that a=b or b=c or a=c. if u r to show it is a right angled triangle u should show pythagoras theorem is valid. \[a\cos A=b\cos B\] \[a* \frac{ b^2+c^2a^2 }{ 2bc}=b*\frac{ a^2+c^2b^2 }{ 2ac }\] vat do u get when u simplify this? @AonZ

AonZ
 one year ago
Best ResponseYou've already chosen the best response.02c^3 a^2  2a^4 c  2c^3 b^2 + 2b^4 c = 0

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2u can factor out 2c.

AonZ
 one year ago
Best ResponseYou've already chosen the best response.02c ( b^4  c^2 b^2 + a^2 c^2  a^4) = 0 this right so far?

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2yup:) good:) nw divide by 2c both sides.

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0ok done that. btw im writing it down

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2u will get this. b^4  c^2 b^2 + a^2 c^2  a^4=0 try to factorise this.

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0(b^2  a^2)(b^2 +a^2 c^2)

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0(b+a)(ba)(b^2+a^2  c^2)

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2(b+a)(ba)(b^2+a^2  c^2)=0 Divide by (b+a)(ba) both sides. vat do u get?

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0you can tell its right angle by looking at this.. but how do you tell if its isosceles?

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2u r nt asked to prove both right? either one of that?

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0i still think it means to prove that the triangle must be right or isoscles but it cant be scalene

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0but can we show it isoscles anyways?

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2let me think. hav to go nw. will be back in 15 mnts

gohangoku58
 one year ago
Best ResponseYou've already chosen the best response.1(b+a)(ba)(b^2+a^2  c^2) =0 gives (b+a)=0 OR (ba)= 0 OR (b^2+a^2  c^2)=0 so, ba = 0 >a=b>isosceles (b^2+a^2  c^2)=0 >right as you already know.

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0ohh xDDDD THANKS!! Shame i can only give medal to 1 person :(

gohangoku58
 one year ago
Best ResponseYou've already chosen the best response.1hey, i am not here for medals ;)

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2Welcome:) you can give it to @gohangoku58

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2cos he/she deserves it most:)

gohangoku58
 one year ago
Best ResponseYou've already chosen the best response.1:O You made him solve the whole thing and i deserve it!??

ajprincess
 one year ago
Best ResponseYou've already chosen the best response.2yup:) it was u who pointed out the isoscles one:)
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