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MX2 Marathon (4 Viewers)

HazzRat

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what bs is this. Can someone plz explain to me how these r equal
rh534tgerhtrg4r.PNG
 
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liamkk112

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what bs is this. Can someone plz explain to be how these r equal
View attachment 42231
if z-1/z+1 is purely imaginary, then the real part is zero, aka that x(x+1) + y(y-1) = 0
=> x^2 + x + y^2 - y = 0
=> x^2 + x + 1/4 + y^2 - y + 1/4 = 1/4 + 1/4 (completing the square)
=> (x+1/2)^2 + (y-1/2)^2 = 1/2
so basically it should be = 1/2, u can see they made a mistake because they noted that radius is 1/sqrt(2) which makes sense if
(x+1/2)^2 + (y-1/2)^2 = 1/2
 

liamkk112

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if z-1/z+1 is purely imaginary, then the real part is zero, aka that x(x+1) + y(y-1) = 0
=> x^2 + x + y^2 - y = 0
=> x^2 + x + 1/4 + y^2 - y + 1/4 = 1/4 + 1/4 (completing the square)
=> (x+1/2)^2 + (y-1/2)^2 = 1/2
so basically it should be = 1/2, u can see they made a mistake because they noted that radius is 1/sqrt(2) which makes sense if
(x+1/2)^2 + (y-1/2)^2 = 1/2
also there should be an open circle at (-1, 0) as this would make the denominator 0
 

Luukas.2

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also there should be an open circle at (-1, 0) as this would make the denominator 0
And is also impossible, as it makes

which is not purely imaginary - so two open circles, at opposite ends of a diameter.
 

Luukas.2

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what bs is this. Can someone plz explain to me how these r equal
View attachment 42231
Note that a purely geometric approach would provide the graph, with the points and excluded, and is quicker:


Geometrically, this statement tells us that the angle between the vector from to and the vector from to is a right angle.

Applying the converse of the angle in a semicircle theorem, it follows that lies on one of the two semi-circles whose diameter is the interval joining and .

The two end points of the diameter, and , are excluded from the locus as each results in one of the two vectors being the zero vector, and hence one of the two arguments being and thus undefined.

---

Taking the algebraic approach, the two constraints that lead to points being excluded are that and . The point (-1, 0) violates both constraints, whilst the point (0, 1) violates only the second constraint.
 

HazzRat

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Can someone plz explain to me the second last line of reasoning? That is: z1^2 + z2^2 = z1^2*(1+a^2). How did they get that?
jakaksjfj.PNG
 

ExtremelyBoredUser

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nah i'm a queen 💅
Interdice, this is a man. Yes he is asian but he is not japanese or korean, I can confirm from personal experience, you might be a dwarf in comparison however like a pitbull I am worried you might try to slober all over him. He is a hard working person and has a family to take care of, please do not s** assault this man when you get on UNSW campus, he is simply making a very ironic and funny joke which juxtaposes my claim that he is a king to seem zesty, this does not warrant any abuse.

Much appreciated,
A worried friend of Lith_30
 

HazzRat

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for question (iii) here, where did they get the first statement of the proof from? I could solve the question after getting that statement but like idk where they got it
jnjanwfjwan.PNG
 

liamkk112

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View attachment 42394

for question (iii) here, where did they get the first statement of the proof from? I could solve the question after getting that statement but like idk where they got it
View attachment 42395
in ii) let a^3 = (a^3/1+a^3), b^3 = (b^3 /1+b^3), c^3 = (1/1+c^3) for the first one.
then taking cube roots to get a,b and c u see how the rhs comes about
 

liamkk112

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though i'm not sure what the motivation is for thinking of that specific substitution
 

HazzRat

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For question (ii) here, y is the angle ∠OAC a right angle? I kinda assumed ∠OCA to be the right angle

brgefqwd.PNG
 

Luukas.2

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View attachment 42402
For question (ii) here, y is the angle ∠OAC a right angle? I kinda assumed ∠OCA to be the right angle

View attachment 42403
The right angle is definitely OAC as the tangent to a circle is always perpendicular to the radius at the point of contact.

If OCA was a right angle, then the tangent at A would be parallel to OC and thus OA would not be a tangent, but rather would cross the circle at some point B between O and A... in which case, there must be points on the circle between A and B with a larger principal argument.

 

HazzRat

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solid induction question from my school's 2020 test
 

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