VCE Methods Question Thread!

[keltingmeith]

Question how do you type all the math stuff what app/website do you use?

We use the LaTeX type-setting environments. This website has some handy links to get you started on learning it, if this is your desire. At university, if you ever have to type-up a report that involves mathematics, LaTeX is very much your friend.

Hello!
I'm currently learning the derivative of circular functions. There is a question i don't get. I was wondering if you could help me?


Find the derivative of each of the following with respect to Ө
sin²2Ө

The answer said:
let y= sin²2Ө and u = sin2Ө
then y=u² and applying the chain rule:

dy/dӨ = 2u*2cos2Ө
           = 4sin 2Ө cos 2Ө
           = 2sin4Ө, as sin4Ө = 2sin2Өcos2Ө
the bold bit is what i don't understand. why is sin4Ө = 2sin2Өcos2Ө?

thank you in advance!

This is what we call a double angle formula, which you will learn about when you hit trig functions.

Note that simplifying it to is not necesarry, and you could have left it as

[knightrider]

what does it actually mean when it gives you coords of points such as A(3,0) and B(5,6)

and it says find AB

[keltingmeith]

what does it actually mean when it gives you coords of points such as A(3,0) and B(5,6)

and it says find AB

This sounds very much like a vectors question from specialist... Could you give us the full question, so we can see an example? In truth, this could mean any number of things depending on the context.

[knightrider]

This sounds very much like a vectors question from specialist... Could you give us the full question, so we can see an example? In truth, this could mean any number of things depending on the context.

Thanks eulerfan101
here is  the question.
what does it actually mean when it gives you coords of points such as A(3,0) and B(5,6)
Find the line AB.
Find the magnitude of AB.

[keltingmeith]

Thanks eulerfan101
here is  the question.
what does it actually mean when it gives you coords of points such as A(3,0) and B(5,6)
Find the line AB.
Find the magnitude of AB.

This is not a standard question, it is incredibly weird.

I'm going to assume they mean the line between those points - which case, first we find the gradient:



Then we find the line with our method of choice:



Now, for the second question, we just use the distance between two points formula (i.e., pythag):



Note that the final simplification is optional.

[SE_JM]

Hello, just a quick question.
Are you expected to know the value of sec²0 without a calculator?
I know that we are meant to memorise the values of basic angles of tan, cos, and sin but I don't know if we are meant to memorise the values of basic angles of sec, csc and cot etc. and also because I don't know the values of these....

thank you!

[knightrider]

This is not a standard question, it is incredibly weird.

I'm going to assume they mean the line between those points - which case, first we find the gradient:



Then we find the line with our method of choice:



Now, for the second question, we just use the distance between two points formula (i.e., pythag):



Note that the final simplification is optional.

Thanks Eulerfan101

[pi]

Hello, just a quick question.
Are you expected to know the value of sec²0 without a calculator?
I know that we are meant to memorise the values of basic angles of tan, cos, and sin but I don't know if we are meant to memorise the values of basic angles of sec, csc and cot etc. and also because I don't know the values of these....

thank you!

They are all reciprocal functions, should be easy to figure out

eg. sec(x) = 1/cos(x). Hence sec(pi/4) = 1/cos(pi/4) = 1/(sqrt(2)/2) = 2/sqrt(2) = sqrt(2)

[SE_JM]

They are all reciprocal functions, should be easy to figure out

eg. sec(x) = 1/cos(x). Hence sec(pi/4) = 1/cos(pi/4) = 1/(sqrt(2)/2) = 2/sqrt(2) = sqrt(2)

Hello. Thank you
I completely forgot xD

[keltingmeith]

Hello. Thank you
I completely forgot xD

You don't need to know them to any depth, anyway. In fact, to memory, the methods formula sheet says that the derivative of tan is 1/cos^2(x), not sec^2(x). (it may list both, though)

[SE_JM]

You don't need to know them to any depth, anyway. In fact, to memory, the methods formula sheet says that the derivative of tan is 1/cos^2(x), not sec^2(x). (it may list both, though)

But you wouldn't lose any marks by using sec^2(x), right?
Stupid question, but I had to ask

[keltingmeith]

But you wouldn't lose any marks by using sec^2(x), right?
Stupid question, but I had to ask

Nope - any and all standard alternative notation is good and fair. Just like you won't be penalised for writing u' instead of du/dx, or ln(x) instead of log_e(x).

[SE_JM]

Thanks!

[knightrider]

This may be a bit off topic but how come guests can also post in these posts i thought they could only view as they havent created an account

[RedCapsicum]

Hey can someone help me with this question

A car travels half a distance of its journey at an average speed of 80km/h and half at an average speed of xkm/h
Define a function S which gives the average speed for the total journey as a function of x