Maths Methods 3/4 Help Thread 2011

[jasoN-]

[luken93]

If , then what does y equal?

[Tobias Funke]

Find the magnitude of An acute angle between the lines 2y + 3x = 4 and x + y = 5

I looked at this and gave it a go, but I still dont know how to do it

[xZero]

y = -x + 5  (line 1)
y = (4-3x)/2, y = -3x/2 + 2   (line 2)

find the angle (theta 1) between line 1 with the x-axis, do the same with line 2 (theta 2). The difference between the 2 angle will be the angle between the 2 lines.

(If you're unclear, graph the 2 lines and draw theta 1 and theta 2)

[thushan]

Draw these two lines on a set of cartesian axes, find the angle between each line and the x-axis (acute angle = arctan(absolute value of gradient)). Draw them in the diagram, then use geometry to find the angle btwn lines.

EDIT: what xZero said.

[Andiio]

Is finding the angle between lines within the methods course?

[luffy]

Is finding the angle between lines within the methods course?

Its a fairly basic concept and can definitely come up in methods. However, it is basic geometry and shouldn't be too difficult to do.

[luken93]

Is finding the angle between lines within the methods course?

Yeah, as luffy said it's fairly easy, however it's important to remember that you can use the gradient rather than finding the intercepts as they are essentially the same thing, rise/run.

If only I had realised that instead of wasting time finding the intercepts to make a triangle...

[Water]

Is finding the angle between lines within the methods course?

Its a touched on concept, thats fitted in 1/5th of a page. Lol, if you count that in as a course, then sure. But its common sense, I'd suspect.

[kefoo]

hey guys question here...
A solution for x in log3(4-11x) = 4 is:

[pi]

[xZero]

Edit: Ninja'd

[kefoo]

thanks guys really making my holidays less stressful
got another one..
sqrt3tan(x) = 3
Find the general solution

what i did was get tan(x) = 1/sqrt3
which is pi/6
then i put it in the general solution which then i got..
npi + pi/6
which is incorrect =.=

[luffy]

thanks guys really making my holidays less stressful
got another one..
sqrt3tan(x) = 3
Find the general solution

what i did was get tan(x) = 1/sqrt3
which is pi/6
then i put it in the general solution which then i got..
npi + pi/6
which is incorrect =.=

Don't worry - you simply made a calculation error... No concept errors, which is a good thing.

This is my working out - Hopefully, I didn't make any errors myself xD.





-> That was your calculation error.

, where

Hope I helped.

[kefoo]

oh thanks luffy

edit: forgot to add yet another q =.=

Find the first two positive solutions to this eqn
2cos(2x) = sqrt(3)

Well what i tried was I solved for x which I got
2x = pi/6
x = pi/12
and since cos is + in the first quadrant pi/12 is a solution
then i did 2pi - pi/12 to get the 2nd one since cos is + in the 4th q, but the answer said it was 11pi/12 which is what you get if you do pi - pi/12 (which cos is negative in?)