Given the angle between planes $pi_1$ and $pi_2$ is equal to the angle between…

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I'm not sure where I'm going wrong with this question but i keep coming to a hexic equation rather than a quartic equation.



the three planes:
$$pi_1: ax+2y+z=3$$
$$pi_2: x+ay+z=4$$
$$pi_3: x+y+az=5$$



Given the angle between planes $pi_1$ and $pi_2$ is equal to the angle between $pi_2$ and $pi_3$, show that $a$ must statisfy the quartic equation
$$5a^4+2a^3-2a^2-8a-3=0$$










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  • If you’d like someone to point out where you’re going wrong, then you should show your work.
    – amd
    Sep 10 at 20:15














up vote
0
down vote

favorite












I'm not sure where I'm going wrong with this question but i keep coming to a hexic equation rather than a quartic equation.



the three planes:
$$pi_1: ax+2y+z=3$$
$$pi_2: x+ay+z=4$$
$$pi_3: x+y+az=5$$



Given the angle between planes $pi_1$ and $pi_2$ is equal to the angle between $pi_2$ and $pi_3$, show that $a$ must statisfy the quartic equation
$$5a^4+2a^3-2a^2-8a-3=0$$










share|cite|improve this question





















  • If you’d like someone to point out where you’re going wrong, then you should show your work.
    – amd
    Sep 10 at 20:15












up vote
0
down vote

favorite









up vote
0
down vote

favorite











I'm not sure where I'm going wrong with this question but i keep coming to a hexic equation rather than a quartic equation.



the three planes:
$$pi_1: ax+2y+z=3$$
$$pi_2: x+ay+z=4$$
$$pi_3: x+y+az=5$$



Given the angle between planes $pi_1$ and $pi_2$ is equal to the angle between $pi_2$ and $pi_3$, show that $a$ must statisfy the quartic equation
$$5a^4+2a^3-2a^2-8a-3=0$$










share|cite|improve this question













I'm not sure where I'm going wrong with this question but i keep coming to a hexic equation rather than a quartic equation.



the three planes:
$$pi_1: ax+2y+z=3$$
$$pi_2: x+ay+z=4$$
$$pi_3: x+y+az=5$$



Given the angle between planes $pi_1$ and $pi_2$ is equal to the angle between $pi_2$ and $pi_3$, show that $a$ must statisfy the quartic equation
$$5a^4+2a^3-2a^2-8a-3=0$$







plane-geometry






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asked Sep 10 at 18:52









H.Linkhorn

358




358











  • If you’d like someone to point out where you’re going wrong, then you should show your work.
    – amd
    Sep 10 at 20:15
















  • If you’d like someone to point out where you’re going wrong, then you should show your work.
    – amd
    Sep 10 at 20:15















If you’d like someone to point out where you’re going wrong, then you should show your work.
– amd
Sep 10 at 20:15




If you’d like someone to point out where you’re going wrong, then you should show your work.
– amd
Sep 10 at 20:15










1 Answer
1






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up vote
0
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Given the planes



$$
pi_k to left<p-p_k,vec n_kright> = 0
$$



with $p = (x,y,z)$



if



$$
fracleft< vec n_1,vec n_2right> ^2 = fracleft< vec n_2,vec n_3right> ^2
$$



then



$$
5a^4+2a^3-2a^2-8a-3 = 0
$$



here $left<cdot,cdotright>$ represents the scalar product of two vectors






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  • what does the first line mean? I'm not very good with notation
    – H.Linkhorn
    Sep 10 at 19:30










  • @H.Linkhorn For the first plane we have $vec n_1 = (a,2,1)$ and $p_1 = (0,0,3)$
    – Cesareo
    Sep 10 at 20:14










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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
0
down vote













Given the planes



$$
pi_k to left<p-p_k,vec n_kright> = 0
$$



with $p = (x,y,z)$



if



$$
fracleft< vec n_1,vec n_2right> ^2 = fracleft< vec n_2,vec n_3right> ^2
$$



then



$$
5a^4+2a^3-2a^2-8a-3 = 0
$$



here $left<cdot,cdotright>$ represents the scalar product of two vectors






share|cite|improve this answer




















  • what does the first line mean? I'm not very good with notation
    – H.Linkhorn
    Sep 10 at 19:30










  • @H.Linkhorn For the first plane we have $vec n_1 = (a,2,1)$ and $p_1 = (0,0,3)$
    – Cesareo
    Sep 10 at 20:14














up vote
0
down vote













Given the planes



$$
pi_k to left<p-p_k,vec n_kright> = 0
$$



with $p = (x,y,z)$



if



$$
fracleft< vec n_1,vec n_2right> ^2 = fracleft< vec n_2,vec n_3right> ^2
$$



then



$$
5a^4+2a^3-2a^2-8a-3 = 0
$$



here $left<cdot,cdotright>$ represents the scalar product of two vectors






share|cite|improve this answer




















  • what does the first line mean? I'm not very good with notation
    – H.Linkhorn
    Sep 10 at 19:30










  • @H.Linkhorn For the first plane we have $vec n_1 = (a,2,1)$ and $p_1 = (0,0,3)$
    – Cesareo
    Sep 10 at 20:14












up vote
0
down vote










up vote
0
down vote









Given the planes



$$
pi_k to left<p-p_k,vec n_kright> = 0
$$



with $p = (x,y,z)$



if



$$
fracleft< vec n_1,vec n_2right> ^2 = fracleft< vec n_2,vec n_3right> ^2
$$



then



$$
5a^4+2a^3-2a^2-8a-3 = 0
$$



here $left<cdot,cdotright>$ represents the scalar product of two vectors






share|cite|improve this answer












Given the planes



$$
pi_k to left<p-p_k,vec n_kright> = 0
$$



with $p = (x,y,z)$



if



$$
fracleft< vec n_1,vec n_2right> ^2 = fracleft< vec n_2,vec n_3right> ^2
$$



then



$$
5a^4+2a^3-2a^2-8a-3 = 0
$$



here $left<cdot,cdotright>$ represents the scalar product of two vectors







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Sep 10 at 19:23









Cesareo

6,2192413




6,2192413











  • what does the first line mean? I'm not very good with notation
    – H.Linkhorn
    Sep 10 at 19:30










  • @H.Linkhorn For the first plane we have $vec n_1 = (a,2,1)$ and $p_1 = (0,0,3)$
    – Cesareo
    Sep 10 at 20:14
















  • what does the first line mean? I'm not very good with notation
    – H.Linkhorn
    Sep 10 at 19:30










  • @H.Linkhorn For the first plane we have $vec n_1 = (a,2,1)$ and $p_1 = (0,0,3)$
    – Cesareo
    Sep 10 at 20:14















what does the first line mean? I'm not very good with notation
– H.Linkhorn
Sep 10 at 19:30




what does the first line mean? I'm not very good with notation
– H.Linkhorn
Sep 10 at 19:30












@H.Linkhorn For the first plane we have $vec n_1 = (a,2,1)$ and $p_1 = (0,0,3)$
– Cesareo
Sep 10 at 20:14




@H.Linkhorn For the first plane we have $vec n_1 = (a,2,1)$ and $p_1 = (0,0,3)$
– Cesareo
Sep 10 at 20:14

















 

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