Complex Modulus Question

Original post by RDKGames

The cusp occurs when the stuff inside the modulus part is zero. In this question, this is when

x+4 = 0

.

Part b doesnt require you to find the inverse. It asks you to explain why it doesn't exist... Think about what kind of mapping a function needs to be in order for it to have an inverse.

so the cusp is still at x = -4

Reply 3

so the range would be f(x) < 8

Original post by Hollymae764

so the cusp is still at x = -4

Reply 4

Original post by RDKGames

The cusp occurs when the stuff inside the modulus part is zero. In this question, this is when

x+4 = 0

.

Part b doesnt require you to find the inverse. It asks you to explain why it doesn't exist... Think about what kind of mapping a function needs to be in order for it to have an inverse.

It would have to be reflected in y = x and since the function is a modulus this cannot happen. Is that correct?

Reply 5

Original post by Hollymae764

so the range would be f(x) < 8

Yes with

\leq

and not

<

.

You do not need to use x=-4 here at all. Since the modulus is always non-negative, it means that

|x-4| \geq 0

-\dfrac{5}{3}|x-4| \leq 0

-\dfrac{5}{3}|x-4| + 8 \leq 8

Reply 6

Original post by Hollymae764

It would have to be reflected in y = x and since the function is a modulus this cannot happen. Is that correct?

That's not it. You have four mappings;

One-to-one
One-to-many
Many-to-one
Many-to-many

Which one can have an inverse? Which one does the modulus function correspond to?

Reply 7

Original post by RDKGames

That's not it. You have four mappings;

One-to-one
One-to-many
Many-to-one
Many-to-many

Which one can have an inverse? Which one does the modulus function correspond to?

ohhh this is a many to one function and the inverse of it would be one to many which means it cant be a function

Reply 8

Original post by Hollymae764

ohhh this is a many to one function and the inverse of it would be one to many which means it cant be a function

Er.. close, one to many mappings are not functions to begin with, so no point trying to talk about inverse of this type of mapping.

Reply 9

Original post by RDKGames

Er.. close, one to many mappings are not functions to begin with, so no point trying to talk about inverse of this type of mapping.

Im confused how is the modulus a one to many graph? I thought it was many to one?

Reply 10