Linear Algebra: orthogonality in $mathbb{R}^{3}$












0














$$v_{1} = (1, 1, 1)$$



$$v_{2} = (-1, 1, 0)$$



$$v_{3} = (-1, -1, 2)$$



The vectors $v1$, $v2$, and $v3$ form an orthogonal basis for $mathbb{R}^{3}$.



If $w = (4, -2, 4)$, then what is the coordinate vector, $[w]_{B}$, of $w$ with respect to the basis $B = {v1, v2, v3}$










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    Dec 9 at 3:43
















0














$$v_{1} = (1, 1, 1)$$



$$v_{2} = (-1, 1, 0)$$



$$v_{3} = (-1, -1, 2)$$



The vectors $v1$, $v2$, and $v3$ form an orthogonal basis for $mathbb{R}^{3}$.



If $w = (4, -2, 4)$, then what is the coordinate vector, $[w]_{B}$, of $w$ with respect to the basis $B = {v1, v2, v3}$










share|cite|improve this question
























  • Welcome to math.se. Here are some tips on how to ask a good question.
    – André 3000
    Dec 9 at 3:43














0












0








0







$$v_{1} = (1, 1, 1)$$



$$v_{2} = (-1, 1, 0)$$



$$v_{3} = (-1, -1, 2)$$



The vectors $v1$, $v2$, and $v3$ form an orthogonal basis for $mathbb{R}^{3}$.



If $w = (4, -2, 4)$, then what is the coordinate vector, $[w]_{B}$, of $w$ with respect to the basis $B = {v1, v2, v3}$










share|cite|improve this question















$$v_{1} = (1, 1, 1)$$



$$v_{2} = (-1, 1, 0)$$



$$v_{3} = (-1, -1, 2)$$



The vectors $v1$, $v2$, and $v3$ form an orthogonal basis for $mathbb{R}^{3}$.



If $w = (4, -2, 4)$, then what is the coordinate vector, $[w]_{B}$, of $w$ with respect to the basis $B = {v1, v2, v3}$







linear-algebra orthogonality






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edited Dec 9 at 4:31









dantopa

6,40932042




6,40932042










asked Dec 8 at 23:25









bradp

1




1












  • Welcome to math.se. Here are some tips on how to ask a good question.
    – André 3000
    Dec 9 at 3:43


















  • Welcome to math.se. Here are some tips on how to ask a good question.
    – André 3000
    Dec 9 at 3:43
















Welcome to math.se. Here are some tips on how to ask a good question.
– André 3000
Dec 9 at 3:43




Welcome to math.se. Here are some tips on how to ask a good question.
– André 3000
Dec 9 at 3:43










1 Answer
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oldest

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1














Suppose



$$(4,-2,4)=w=av_1+bv_2+cv_3implies langle v_1,wrangle = 3a_1$$



Can you now complete the deduction? Can you see why having an orthonormal basis makes things even easier than the above?






share|cite|improve this answer





















  • what do you mean by this?
    – bradp
    Dec 8 at 23:43










  • Where did the 3a1 come from?
    – bradp
    Dec 8 at 23:46










  • ok so I think i know where you got 3a1 from. did you just do the dot product of v1 with itself? Then repeated this to find b and c?
    – bradp
    Dec 8 at 23:55










  • @bradp Yes, but with $;v_2,v_3;$ the dot product is zero...
    – DonAntonio
    Dec 9 at 0:51











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1 Answer
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active

oldest

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1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









1














Suppose



$$(4,-2,4)=w=av_1+bv_2+cv_3implies langle v_1,wrangle = 3a_1$$



Can you now complete the deduction? Can you see why having an orthonormal basis makes things even easier than the above?






share|cite|improve this answer





















  • what do you mean by this?
    – bradp
    Dec 8 at 23:43










  • Where did the 3a1 come from?
    – bradp
    Dec 8 at 23:46










  • ok so I think i know where you got 3a1 from. did you just do the dot product of v1 with itself? Then repeated this to find b and c?
    – bradp
    Dec 8 at 23:55










  • @bradp Yes, but with $;v_2,v_3;$ the dot product is zero...
    – DonAntonio
    Dec 9 at 0:51
















1














Suppose



$$(4,-2,4)=w=av_1+bv_2+cv_3implies langle v_1,wrangle = 3a_1$$



Can you now complete the deduction? Can you see why having an orthonormal basis makes things even easier than the above?






share|cite|improve this answer





















  • what do you mean by this?
    – bradp
    Dec 8 at 23:43










  • Where did the 3a1 come from?
    – bradp
    Dec 8 at 23:46










  • ok so I think i know where you got 3a1 from. did you just do the dot product of v1 with itself? Then repeated this to find b and c?
    – bradp
    Dec 8 at 23:55










  • @bradp Yes, but with $;v_2,v_3;$ the dot product is zero...
    – DonAntonio
    Dec 9 at 0:51














1












1








1






Suppose



$$(4,-2,4)=w=av_1+bv_2+cv_3implies langle v_1,wrangle = 3a_1$$



Can you now complete the deduction? Can you see why having an orthonormal basis makes things even easier than the above?






share|cite|improve this answer












Suppose



$$(4,-2,4)=w=av_1+bv_2+cv_3implies langle v_1,wrangle = 3a_1$$



Can you now complete the deduction? Can you see why having an orthonormal basis makes things even easier than the above?







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Dec 8 at 23:37









DonAntonio

176k1491225




176k1491225












  • what do you mean by this?
    – bradp
    Dec 8 at 23:43










  • Where did the 3a1 come from?
    – bradp
    Dec 8 at 23:46










  • ok so I think i know where you got 3a1 from. did you just do the dot product of v1 with itself? Then repeated this to find b and c?
    – bradp
    Dec 8 at 23:55










  • @bradp Yes, but with $;v_2,v_3;$ the dot product is zero...
    – DonAntonio
    Dec 9 at 0:51


















  • what do you mean by this?
    – bradp
    Dec 8 at 23:43










  • Where did the 3a1 come from?
    – bradp
    Dec 8 at 23:46










  • ok so I think i know where you got 3a1 from. did you just do the dot product of v1 with itself? Then repeated this to find b and c?
    – bradp
    Dec 8 at 23:55










  • @bradp Yes, but with $;v_2,v_3;$ the dot product is zero...
    – DonAntonio
    Dec 9 at 0:51
















what do you mean by this?
– bradp
Dec 8 at 23:43




what do you mean by this?
– bradp
Dec 8 at 23:43












Where did the 3a1 come from?
– bradp
Dec 8 at 23:46




Where did the 3a1 come from?
– bradp
Dec 8 at 23:46












ok so I think i know where you got 3a1 from. did you just do the dot product of v1 with itself? Then repeated this to find b and c?
– bradp
Dec 8 at 23:55




ok so I think i know where you got 3a1 from. did you just do the dot product of v1 with itself? Then repeated this to find b and c?
– bradp
Dec 8 at 23:55












@bradp Yes, but with $;v_2,v_3;$ the dot product is zero...
– DonAntonio
Dec 9 at 0:51




@bradp Yes, but with $;v_2,v_3;$ the dot product is zero...
– DonAntonio
Dec 9 at 0:51


















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