Dekoyl's question thread

[Glockmeister]

remember that change of base rule
 

So

[Collin Li]

Second one is correct mate:





Then using the special case of the change of base law, you get:



Hence,

So I'm assuming it was a multi-choice. It was your error that led you to believe the first one was correct, but that one was actually wrong (see my post above).

[dekoyl]

Yes indeed it's a multiple choice question.

Thanks Coblin and Glock.

[dekoyl]

If a question asks you to find a probability to 3 decimal places, (let p = 0.198), do they want you to use p = 0.199 from thereon in the question or should I use 0.198621.. to be on the safe side?

Thanks.

[bec]

I'm not too sure what you mean...are you talking about when a question is in parts a, b, c etc and one of the parts asks you to round something to 3 decimal places?
If so - you need to round it up or down, not just chop it off after the 3 dp. (eg, in the example you gave, 0.198621, you'd round that to 0.199, not 0.198).

If you need to use the value again in calculations later on, just keep it at the accuracy that you've got on your calculator. In my workings, I show an extra decimal place too.

Is that what you meant?

[dekoyl]

I'm not too sure what you mean...are you talking about when a question is in parts a, b, c etc and one of the parts asks you to round something to 3 decimal places?
If so - you need to round it up or down, not just chop it off after the 3 dp. (eg, in the example you gave, 0.198621, you'd round that to 0.199, not 0.198).

If you need to use the value again in calculations later on, just keep it at the accuracy that you've got on your calculator. In my workings, I show an extra decimal place too.

Is that what you meant?

Yes that was what I meant. Yeah I had meant 0.199
Thanks for the quick response.

[bec]

haha yeah I thought it might've been a typo but I didn't want to offend you if it wasn't!

[dekoyl]

Did I take on this question with the wrong method? If not, how do I "see other possible solutions"?
{} *INTERSECTION* {}

When I did it, I reduced it to:

And then settled with 2 solutions.

However there was also:

which yields another 2 solutions.. I wouldn't have noticed this

Thank you.

[Quickclaw]

you can't simply divide by cos(x) it as you are eliminating more solutions so you are missing the cos(x)=0 

[nerd]

I think Quickclaw meant you CAN'T divde, cause you are eliminating some of the possible answers!

[Quickclaw]

whoops sorry =(

[Mao]

at the point you divided by cos(x), [assuming that's what you did first]
the next line should be:

or

the eqn on the left assumes that cos(x)=/=0, hence a separate equation need to be set out on the right to prove such. =]

[dekoyl]

Thanks Mao. I understand now.

I thank you too, Quickclaw and nerd

[dekoyl]

1. I think I asked in someone's thread but I forgot which one. I wanted to know if adding "+c" when asked to find an antiderivative would technically be wrong?

2.What is the range of with a domain of ? I'm not too sure how to work it out as I'm unfamiliar with the graph's shape. This a non-calculator question.

Thanks.

[fredrick]

1)adding the +c when finding an antiderivative is not wrong and you should not lose any marks for it. (according to MAV exam solutions for one of the exams)

2)The period is so you know all the values it can take will be inside the domain specified. is positive for all x, furthermore the range can take is [0,1]. So the range is [-8,1].