question (1 Viewer)

[mojako]

Hello..
Can you do part (c) pls

In the picture, ABD and AJK are two isosceles triangles, right angled at A.
(a) Show that angle BJA = angle DKA
(b) BJ is produced to meet DK at X. Show that BX is perpendicular to DK
(c) The square ABCD is completed. Show that angele BXC = 45 degrees

I feel bad making a post just to ask question, hehe

EDIT: pls go straight to the last few posts

 

[ngai]

In the picture, ABD and AJK are two isosceles triangles, right angled at A.

picture?
where it is?

 

[mojako]

well... its here!

I presses the Submit button then I realised I didnt put the pic and pressed the browser stop button before the page changes, then uploaded the pic.. then pressed submit again.. but the attachment didnt come

 

[ngai]

haha use the lead ups
BXDC cyclic (angle X = angle C = 90, opposite angles supplementary)
so angle BXC = angle BDC = 45 (angle at circumference ...)

 

[mojako]

haha use the lead ups
BXDC cyclic (angle X = angle C = 90, opposite angles supplementary)
so angle BXC = angle BDC = 45 (angle at circumference ...)

ur smart
(or maybe im stupid )

 

[mojako]

Another question:
This question asks to factorise z^3 + 8 over (a) real field and (b) complex field.
Then it says "let w be one of the complex roots of z^3 + 8 = 0".
Then it asks, "show that w^2 = 2w - 4"
Will I get the mark if I just substitute w = root#1 to verify, then do the same thing with w = root#2?
The proper way is to say that from the previous part,
z^3 + 8 = (z + 2) (z^2 - 2z + 4)
so w^2 - 2w + 4 = 0

And.. a 3U question from CSSA 2003 trial:
find lim(n->infinity) of 5(10^n)+3 on 2(10^n)+1 (2 marks)
Solution says: 1 mark for rearranging limit and 1 mark for finding answer
Will I get 2 marks if I just say it's 5/2 since the "3" and "1" in the expression don't affect the value significantly when n is infinitely large?

 

[mervvyn]

for the first question, you may be able to get away with it as it's a "show" not a "prove" and i seem to remember my teacher saying you could use the given answer in a "show" qn... i'll leave that for someone else.

for the second, i would say that you might get the mark, depending on the teacher's mood. what you are saying by looking at an infinitely large n can be shown by dividing the whole expression by (10^n)/(10^n) - the rearrange part - and then taking the limit as n -> inifinity - and now the 3 and the 1 become insignificant, giving the answer as 5/2. It's similar to what you said but a little more rigorous.