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~~Mathematics Revising Game~~ (1 Viewer)

Graceofgod

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lyounamu

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Graceofgod said:
9bi) t = 0 to t = 10

ii) t = 25 to t = 30

iii) t = 10

iv) t = 30

v) t = 20

vi) ...How?

Question:
Prove that:

Root[(cos^2(x) + sin^2(x) + cot^2(x))*sin^2(x)] = 1
well done - all correct except vi but you cannot really post that up here anyway.

your q: doesn't work.
 

tommykins

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回复: Re: ~~Mathematics Revising Game~~

thought so, it wasn't just my shitty working via computer ^^
 

Graceofgod

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Woops =S Sorry must have made mistake =S Should i post another?

EDIT: I am pretty sure it works... =S

EDIT: Yeah I couldn't do it on computer is what I meant.
My question: It is relatively simple, are you sure you aren't messing up the grouping symbols?
 
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tommykins

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回复: Re: ~~Mathematics Revising Game~~

tried it again, doens't work.
 

lyounamu

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Graceofgod said:
Woops =S Sorry must have made mistake =S Should i post another?

EDIT: I am pretty sure it works... =S

EDIT: Yeah I couldn't do it on computer is what I meant.
My question: It is relatively simple, are you sure you aren't messing up the grouping symbols?
that doesn't work because i got this in the end:

root (1+cos^2(x))

and that is NOT equal to 1.
 

Graceofgod

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Re: 回复: Re: ~~Mathematics Revising Game~~

Root[(cos^2(x) + sin^2(x) + cot^2(x))*sin^2(x)] = 1

LHS = Root[(cos^2(x) + sin^2(x) + cot^2(x))*sin^2(x)]
= Root[(1 + cot^2x)sin^2(x)]
= Root(sin^2(x) + cos^2(x))
= Root(1)
= 1
 

lyounamu

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Re: 回复: Re: ~~Mathematics Revising Game~~

Graceofgod said:
Root[(cos^2(x) + sin^2(x) + cot^2(x))*sin^2(x)] = 1

LHS = Root[(cos^2(x) + sin^2(x) + cot^2(x))*sin^2(x)]
= Root[(1 + cot^2x)sin^2(x)]
= Root(sin^2(x) + cos^2(x))
= Root(1)
= 1
ah ok, I think both of us got confused with your sign use.
 

tommykins

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回复: Re: 回复: Re: ~~Mathematics Revising Game~~

Graceofgod said:
Root[(cos^2(x) + sin^2(x) + cot^2(x))*sin^2(x)] = 1

LHS = Root[(cos^2(x) + sin^2(x) + cot^2(x))*sin^2(x)]
= Root[(1 + cot^2x)sin^2(x)]
= Root(sin^2(x) + cos^2(x))
= Root(1)
= 1
cos^2x+sin^2x = 1, not sin^2x.

NVM i see the grouping now.
 
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pLuvia

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Re: 回复: Re: 回复: Re: ~~Mathematics Revising Game~~

Check out this thread for a lot of practice questions for you current HSCers or anyone interested

Marathon 1

From the last question from that thread

Stephen has a loan of 100,000.00 to pay. each month, interest of 0.8% is charged on the outstanding amount
a) If stephen pays 5,000 each month starting one month from now how long will it take him to repay the loan?
b) Now suppose stephen pays different amounts every months, but according to the rule that for every dollar of the balance, he'll pay eight cents, so he'll pay more initially, but less later. Find the outstanding amount after the n-th payment
 

duy.le

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that is a very hard 2 unit question. it was really confusing and i got it wrong... wow that was a bit queer.

note i was referring to lyounamu's question.
 
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Shadose

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Timothy.Siu

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Re: 回复: Re: 回复: Re: ~~Mathematics Revising Game~~

pLuvia said:
Check out this thread for a lot of practice questions for you current HSCers or anyone interested

Marathon 1

From the last question from that thread

Stephen has a loan of 100,000.00 to pay. each month, interest of 0.8% is charged on the outstanding amount
a) If stephen pays 5,000 each month starting one month from now how long will it take him to repay the loan?
b) Now suppose stephen pays different amounts every months, but according to the rule that for every dollar of the balance, he'll pay eight cents, so he'll pay more initially, but less later. Find the outstanding amount after the n-th payment
for a)i got 23.0726 --->24 months
doesn't seem right maybe

time for b, i'll assume he starts paying from month 1
i got nth month=PRn(1-Q)n
where P=$100 000 R=1.008 and Q=0.08
 
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duy.le

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Shadose said:
So how do you do it?

(i) d@/dt=2
@=2t+C
@=2t

(ii)tan(@)=x/10
x=10tan(@)
=10tan2t

(iii)when @=30
t=15s

dx/dt=20sec^2(@)
=20sec^230
=20 x 4/3 km/s ... :S
=80/3 x 3600
=96 000 km/hour o_O Its wrong.... I' know ... I looked at the answers :p
yeah thats what i got, except i got u=75 +2/(3sqr 3)
 

tommykins

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回复: Re: ~~Mathematics Revising Game~~

you need to do d@/dt in radians i believe.
 

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