jinny1's Specialist Questions Thread :D

[jinny1]

Hi,first up it's a pretty simple question what am i doing wrong here??

Q25. Find the y-intercept of the ellipse with equation  [(x-1)^2]/4 + [(y-2)^2]/9

1/4 + [(y-2)^2]/9 = 1

(Square root all terms)

1/2 + (y-2)/3 = 1

(y-2)/3 = 1/2

y-2 = 3/2

y= 7/2

However the solutions page in A+ notes tells me the answer is y = 2 +/- 3root3/2

what's my mistakkee? thanks

[vea]

The step where you square root all terms is wrong, you can't just square root something like that.

Here is the solution though.













Does anyone know what the tex is for the + and minus sign is?

[Mao]

[kamil9876]

(most of the time, unless you have something like )

e.g: if , then but

[jinny1]

oh lol my bad... fail

dw guys i got 99.95_for_sure as my tutor so hopefully things will improve..

A+ notes are damn hard compared to heinemann... i thought spesh was a breeze when i was doing heinemann

oh also how do u write maths equations on this forum??? mine looks confusing

[Hutchoo]

Jinny, we share the same tutor.

[jinny1]

yay

He's got the maddest car... just needs bigger rims though

[Hutchoo]

He does burnouts in my driveway.

[kamil9876]

Does anyone know what the tex is for the + and minus sign is?

Code: [Select]

\pm

[jinny1]

hi guys im just wondering what the simplest,easiest and fastest way to spilt up a trig term so that i can use compound angle formulas...


like sec (pi/12)

or anything else like

5pi/6

7pi/12

3pi/8

or any other random terms like those...

thanks

[luken93]

Usually you can kinda pick them, I don't think there is any "good" way of doing them:
pi/12 = pi/3 - pi/4
5pi/6 = pi/3 + pi/2
7pi/12 = pi/3 + pi/4

[vea]

Such a skill only comes with LOTS of practice and familiarity of the questions.

[jinny1]

awwwww/ i thought there was some magic formula or trick

[soopertaco]

I don't know if this is a trick necessarily because it just using fractions. I just worked this out the other day --" dont know why i didn't see it earlier haha you see instead of trying to find these angles from the 'special' angles (pi/4,pi/3,pi/6,etc) you just use common sense

5pi/6 = (3pi/6) + (2pi/6)
what do we get?
simplified
=(pi/2) + (pi/3)
and voila sub it right into a compound angle formula

same with this one:
7pi/12 = (4pi/12) + (3pi/12) = (pi/3) + (pi/4)

3pi/8 => well for this one; you can't simplify it out like the others so you may have to use a double angle formula!

hope that helped

[jinny1]

Thanks scoopertaco that was helpful

anyway im having difficulty in understanding some of the properties of vector dot products, please help

1.k(a (dot) b) = (ka) (dot) b- =a (dot) (kb)
6. a (dot) b = ab if a and b are in the same direction  Think about why this is the case
7. a (dot) b = - ab if a and b are in the opposite direction  Think about why this is the case

sorry if its a bit too hard to read. This is from page 28 of Derrick ha spesh bound ref

thanks