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Mrs Tibble’s Year 11211 comments to Mrs Tibble’s Year 11 |
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just signing in
Thanks Hannah
just signing in, but could i also have help on the homework please, i don’t understand ex.10 K qu 2… how do you know when to expand and when to simplify ??and how do you expand and simplify the surds ?!… i know we went through it in class but i dont understand my notes
Hi Layla,
That was good timing – I’ve just turned on the computer!!
‘Expand’ means ‘ multiply out the bracket/brackets.
‘Simplify’ means ‘tidy it all up’.
In the context of surds, simplifying means writing it in non-surd form if you can.
eg Q2a
√5(3 – √2) = √5 x 3 – √5 x √2 = 3√5 – √5√2 = 3√5 – √10
In the first term, you can’t combine the terms because only one of them is a root. In the 2nd term you can combine the terms because they are roots which are being multiplied. You can’t simplify this term further because 10 isn’t a square number or a multiple of a square number.
Does that help?
JT
thank you very much, i think i can do it now!
hey miss, im abit baffelled on question 3d in the homework, because the quetion says
2 x 8 x 5 (all square rooted) but im not sure how to answer that becuase only 2 is a square ber ( i think) but i dont kknkow what to do with it??
hey miss, im abit baffelled on question 3d in the homework, because the quetion says
2 x 8 x 5 (all square rooted) but im not sure how to answer that becuase only 2 is a square ber ( i think) but i dont kknkow what to do with it??
and also with question 5 when it sayd surd form a/b what does that mean?
Hi Charlie,
Remember you can combine square roots that are multiplied, so these can be collected together. If you look at the numbers before you rush to multiply you’ll see that one product gives a square number, and this makes life a lot easier!
Q3d √2 x √8 x √5 = √16 x √5 = 4√5
Does that help?
JT
Charlie,
Sorry, I forgot the rest of your question.
Q5 is about writing the number as a product such that one of the numbers is square (see your notes)
eg 5a
√90 = √9 x √10 = 3√10
hey miss, just signing in…sorry its a little bit late
Hi Mrs T
do you know what our school email addresses are? Also, i forgot to ask you this in class on Monday, I’m pretty stuck on the homework question 5, Ex. 10J in the homework book. I don’t really know where to begin! Thanks!
Hi Idil,
You’ll need to ask in school about the e-mail addresses. I wouldn’t put it on here anyway in the public domain!!
Q5. These are like the ones we did in class where you have to write the number inside the square root as a product of two numbers, one of which is a square number. You can then root the square number, leaving you with a number x a smaller surd.
eg (a) √90 = √9 x √10 = 3√10
Does that help?
JT
miss im confused on what the scale needs to be for the axis coz i wrote it in my book but then i handed my book in!!!
:S
Hi Charlie,
Have the graph paper ‘portrait’ way round. Do the x axis in the middle 0-400 in 50s like you did with the other graphs.
On the y axis use the heavy lines to go up in 1s. That should give you -7 to +7 I think.
See you tomorrow.
JT
thanks miss, i get it now, it didnt seem o make sense at the time!
hi miss i’ve started the homework from today and just want to check in doing it correctly 1. state the two angles between 0 and 360 using cosine
so i did: cos 0.7 = 0.9999253697
360-0.9999253697= 359.00….
angles= 0.9999253697, 359
am i write so far ??? thank you
Hi Layla,
No you aren’t ‘write’ – or right!!
0.7 is the cos, not the angle. You need to SHIFT cos to get back to the angle – like we were doing in the lesson.
JT
miss im very confused on what im supposed to be doing for th homework?! for ex 15d q 1 are the answers 359.6 ( 360- 0.4) and -0.4 (0-0.4) if not then i am very confused and dont understand what we did in the lesson! :S
Hi Charlie,
Do you mean 15D or 15C? 0.4 is the first value in 15C
Anyway, in 15D first,
the cos of the angles is 0.7 (NB this is the cos NOT THE ANGLE)
If cos x = 0.7
then x = SHIFT cos 0.7 = 45.6 (1dp)
The other angle is therefore 360 – 45.6 = 314.4
Does that help?
Ex 15C is sine which you need to look at your notes for.
JT
but the book said the two angles. so are they 45.6 and 314.4?
Err… yes! Looks like two angles to me lol
PS Use your cos graph to convince yourself: find 0.7 on the y axis and read across to where you meet the curve (twice). It won’t be accurate because it is hand drawn, but it will give you the approx value.
right i think i got it, do you just do the same thingfor the sin aswell?
Similar principle but not the same because of the shifted curve. Look at your notes and use your graph to check your answers.
Positive sine values are OK but negative ones need more steps.
PS tan is easy – just add/subtract 180 to get the 2nd angle.
so for 15f is it
tan x= 0.528
then is it tan- 0.528= 27.8
180- 27.8= 152.2
o and for the cos’ with minus numbers do you add then to 360 or is it still subtracting?
and then so for 15f q5 is the answer 111.4 becuase
tan x= -2.55
tan- (-2.55)= -68.5
180 + (- 68.6)= 111.4
?
Look at your graph!
27.8 is correct, then move up 180 degrees for the angle that has the same tan value.
If cos is negative, you will get an angle between 90 and 180 from the calculator. You need to see how far this is from 180 and go the same distance the other side. Have your graph in front of you all the time to see the symmetry patterns and get rough values of what the answers are.
Tan x = -2.55
Yes, first answer is negative so out of range because Q wants answers between 0 and 360. Add 180 to get in range as you have done, so 111.4 is the first angle. Add 180 again to get the 2nd.
i dont understand my notes for the sin questions? is it pretty much the same thing that we did when doing the cos??
Kind of.
2 cases though.
If sine value is +, you’ll get an acute angle off the calculator. The 2nd angle is 180-the first angle.
If sine value is negative, calculator will give you a negative angle so add 360 to get in range. That gives you the first angle. See how far that angle is from 360 by subtracting, then add your answer to 180 to get the other angle. Again, it is much easier if you keep referring to the graph.
so with the negative number do the answers come out as negative numbers?? (sorry)
Try it and find out!
THANKYOU SO MUCH for all the help miss i really apreciate it!! im finally done! have a nice weekend.
: D
Can I go out to play now??!!
hey miss, just checking im doing the h/w rite… for question 2 do we need to use the cosine rule??
Hi Charlie,
Is this ex 15K? You are given the area of a triangle, so it must be the area formula – the one we were using in the lesson!
JT
but we’re asked to find the missing side? how do youdo that with the area formula?
This is like the example I did in the lesson. Write out the formula, put all the info from the question in the right place in the formula, and the only one you are missing is the one you want to find.
Is the area formula;
a= 1/2mn sinL??
Yes!! A for area lol
K thanx
But miss it doesn’t give you the value for b so how can you work it out without that?
You aren’t trying to work out the area – you’ve been given it!!
So what value of b will make the answer 27?
Q2 Area = 0.5 x a x b x sin98
Put in numbers:
27 = 0.5 x 12 x b x sin98
Tidy up the numbers on the right by putting them into your calculator
27 = Ans x b
so b = 27/Ans
15?
o rite i get it!!! thankyou
hi mrs tibble
i was wondering if you could mark my book on monday and then i correct it for the tuesday because i dont know what answers are right or wrong?
hannah
Hannah,
I teach all day on Monday and have craft club at lunch time so the earliest I could do it is after school.
oh ok well what should i do because i dont know which answers are right or wrong?
sorry for the inconvenience