VCE Methods Question Thread!

[cosine]

Find the points of intersection between 2cosx and sin(x/2) over the domain [0, 2pi] without using a calculator?

[Floatzel98]

Find the points of intersection between 2cosx and sin(x/2) over the domain [0, 2pi] without using a calculator?

I think this is the kind of question where you would have to use the double angle formulas to get it into a 'do-able' form. If you sub that into cos and simplify you should be able to work it out.

I may just have a terrible textbook, but my methods textbook doesn't go over any of this? I've done it in spesh though. Literally the only question in the whole trig identity chapter we were able to figure out by the Pythagorean identity. Does these every actually come up in exams or are they just there for us if we can use them instead of another method?

[StupidProdigy]

Does anyone know if linear approximation is required/examinable?

Yes definetly. It's even on the formula sheet isn't it? I'm not up to this yet but I'm pretty certain

[lzxnl]

I think this is the kind of question where you would have to use the double angle formulas to get it into a 'do-able' form. If you sub that into cos and simplify you should be able to work it out.

I may just have a terrible textbook, but my methods textbook doesn't go over any of this? I've done it in spesh though. Literally the only question in the whole trig identity chapter we were able to figure out by the Pythagorean identity. Does these every actually come up in exams or are they just there for us if we can use them instead of another method?

I think you forgot a factor of 2 there

[Gentoo]

Yes definetly. It's even on the formula sheet isn't it? I'm not up to this yet but I'm pretty certain

It is on the formula sheet. (they often repeat the formula in the question as well)

For what it's worth, VCAA hasn't asked anything about linear approximations in quite a while... ever since they nailed most people in the 2009 Exam 1 for not understanding why approximations over/underestimate.

[cosine]

I think this is the kind of question where you would have to use the double angle formulas to get it into a 'do-able' form. If you sub that into cos and simplify you should be able to work it out.

I may just have a terrible textbook, but my methods textbook doesn't go over any of this? I've done it in spesh though. Literally the only question in the whole trig identity chapter we were able to figure out by the Pythagorean identity. Does these every actually come up in exams or are they just there for us if we can use them instead of another method?

Well it's a calculator question, but I was thinking about how one could show working out for it because it's methods, so I dont think the use of compound angle formulas is actually required. So would we just use a calculator for this question?

[silverpixeli]

Well it's a calculator question, but I was thinking about how one could show working out for it because it's methods, so I dont think the use of compound angle formulas is actually required. So would we just use a calculator for this question?

Yep.

Use of double angle formulas = spesh

knowing that the calculator can use double angle formulas in solving trig equations and that they might affect the simplest form of your answer to a non-double angle formula trig question (and you might get a different answer to the algebraic, methods one) = methods

[I_I]

I have a question guys~ 
Don't solve the first question- I've got that one right- its's just that the second question needs the first question to solve. So yas, I need help with the second question!!!
1. the length of a rectangle of constant area 800 square millimeters is increasing at the rate pf 4 millimeters per second. What is the width of the rectangle at the moment the width is decreasing at the rate of 0.5 millimeters per second?
2. Under the same conditions as the previous question, how fast is the diagonal of the rectangle changing when the width is 20mm?
I got the answer for the second question: 8sqt(5)/5 when the actual answer is 6sqt(5)/5.
Please show me the step-by-step process
Thank you so much!

[knightrider]

In function notation what does the co-domain tell us or do ?

[kinslayer]

In function notation what does the co-domain tell us or do ?

It tells you what the output of the function looks like. The range of a function is always a subset of its codomain.

[I_I]

Hello, I need additional help on related rates
Here's the question:
"A boat passes a fixed buoy at 9am  heading due west at 3 miles per hour. Another boat passes the same buoy at 10 am heading due north at 5 miles per hour. How fast is the distance between the boads changing at 11:30 am?"

Thank you!!

[Apink!]

Hi!
Can someone please help me with this question:
Find the dimensions of the right circular cone of minimum volume V that can be circumscribed about a sphere of radius 8 inches.

Thank you (:

[knightrider]

for the line x=2 why is the domain represented as ?

What does the squiggly line mean outside the 2?

[kinslayer]

for the line x=2 why is the domain represented as ?

What does the squiggly line mean outside the 2?

The braces indicate a set. Technically, a domain is a set, so rather than being equal to 2, which is a number, it is equal to {2}, which is a set that contains the number 2.

[chansena]

How do I solve this?

I know how to do by cas but is it possible without CAS ?


For the following find two values of x in the range 0 ≤ x ≤ 360:
sin x◦ = −0.3

Thanks !