a)CD^2=(0+4)^2+(-3-0)^2+(-5+3)^2=16+9+4=29
CD=√29
б)AC(-4-3;0+5;-3+6)=(-7;5;3)
AC^2=49+25+9=83
AC=√83
DB(3-0;1+3;-4+5)=(3;4;1)
DB^2=9+16+1=26
AC*DB=-7*3+5*4+3*1=-21+20+3=2
AC*DB=AC*DB*cosx
cosx=2/(√83*√26)=2/46.45≈0.04
x≈88 градусов
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Answers & Comments
a)CD^2=(0+4)^2+(-3-0)^2+(-5+3)^2=16+9+4=29
CD=√29
б)AC(-4-3;0+5;-3+6)=(-7;5;3)
AC^2=49+25+9=83
AC=√83
DB(3-0;1+3;-4+5)=(3;4;1)
DB^2=9+16+1=26
AC*DB=-7*3+5*4+3*1=-21+20+3=2
AC*DB=AC*DB*cosx
cosx=2/(√83*√26)=2/46.45≈0.04
x≈88 градусов