Maths Help ASAP (1 Viewer)

[always_smile]

Solve the equation:

2cosx = Square Root 3, where x is greater then 0 and less then 2 pie.

 

[Eagles]

draw the triangle.

cosx = (root 3)/2, 0<.x.<2pi

x = 30, 330 (or pi/6, 11pi/6)

 

[Trev]

2cosx = x^1/2 where 0<x<360
cosx = (x^1/2)/2
basic angle = 30 degrees, since cos is positive answer angle lies in quadrants 1st and 4th.
x = 0 + 30, 360 - 30
= 30, 330.

 

[Eagles]

2cosx = x^1/2 where 0<x<360
cosx = (x^1/2)/2
basic angle = 30 degrees, since cos is positive answer angle lies in quadrants 1st and 4th.
x = 0 + 30, 360 - 30
= 30, 330.

Sif don't mention "all station to central" if ur gonna say that.

 

[~ ReNcH ~]

This is the method my teacher taught me and is the way I've always solved these equations:

2cosx = rt3
.'. cosx = (rt3)/2, >0
The angle whose cos is (rt3)/2 is pi/6 - this should become basic knowledge by the time the trials arrive (if it isn't already)

cosx is +ve in the 1st and 4th quadrants
.'. x = pi/6, x = 2pi-pi/6 = 11pi/6

Very similar to Trev's approach, except explained in more detail.

 

[Trev]

I prefer to have my angles in degrees rather than radians, even in extension 2 questions I don't usually use radians, instead change it to radians at the end of the question. Is this bad 'so to speak' ?

 

[acmilan]

It could get you into trouble working in degrees, especially when the calculations involve things like time.

 

[Trev]

Time? eh... What topic will this be in?

 

[tennille]

Time? eh... What topic will this be in?

Applications of Calculus in the Physical World.

 

[withoutaface]

Degrees dont survive calculus, radians do.

 

[alphatango]

I prefer to have my angles in degrees rather than radians, even in extension 2 questions I don't usually use radians, instead change it to radians at the end of the question. Is this bad 'so to speak' ?

Depends how far you go with maths. If you do maths at uni, you'll probably never do calculations in degrees again. Most, if not all, of the equations, formulae, etc. that you derive and play with use angles in radians (simplest example I can think of atm is the formula for the arc length of a sector, l=r*theta). Given that you're doing Ext 2, yes, you should be working with radians.

IMHO, they should teach radians much, much earlier...by the time you need them, it's not natural to think in terms of radians. I've worked with them for long enough that I think of everything in terms of radians.

 

[Trev]

IMHO, they should teach radians much, much earlier...by the time you need them, it's not natural to think in terms of radians. I've worked with them for long enough that I think of everything in terms of radians.

Yeah, agreed. They should start teaching radians in the preliminary course!

 

[jumb]

Use a calculator.

 

[Trev]

That my son, takes effort.

 

[~ ReNcH ~]

Yeah, agreed. They should start teaching radians in the preliminary course!

They do...
Really, they should begin teaching redians in Yr 8 or Yr 9...I think I started using them in Yr 10 from memory.

Once you use them a lot, you just begin to memorise basic conversions anyway e.g. pi/3, pi/2, pi/6 - things like 2pi/9 etc. are a bit harder, but you can just plug them into a calculator as jumb said...I know it takes effort, but it has to be done

 

[Trev]

They do...
Really, they should begin teaching redians in Yr 8 or Yr 9...I think I started using them in Yr 10 from memory.

Erm... The first time we came across radians was in the first topic of extension 2, complex numbers! Stupid school!

 

[Slidey]

Erm... The first time we came across radians was in the first topic of extension 2, complex numbers! Stupid school!

*Bursts out laughing*

Sorry, Trev, but that is so dodgy of them.

We covered radians informally after the SC and then formally at the start of year 11.

 

[Trev]

Laughing at my crap education, that makes the both of us

 

[~ ReNcH ~]

Erm... The first time we came across radians was in the first topic of extension 2, complex numbers! Stupid school!

Hmm....seems like a rather late introduction. You should have done it when you learnt how to differentiate trig. functions at least, coz you need radians to differentiate/integrate trig. functions properly.

 

[Trev]

Hmm....seems like a rather late introduction. You should have done it when you learnt how to differentiate trig. functions at least, coz you need radians to differentiate/integrate trig. functions properly.

We still haven't learnt to differentiate trig. functions! We just started the trig. functions topic, so I guess we will learn to differentiate them soon. We (extension 2 students....the 2 of us) learnt radians start term four last year, the rest of the extension 1 class just learnt it this week!