# Share your Multiple Choice answers (1 Viewer)

#### LittlerCandy

##### New Member
Mine:

c
b
a
d
c
a
a
c
b
Can't remember what I put, hopefully d

Last edited:

C
b
c
d
a
b
a
c
b
c

1 c
2 d
3 c
4 d
5 c
6 b
7 a
8 d
9 b
10 c

Hahaha

1) c
2) d
3) c
4) d
5) a
6) a
7) a
8) d
9) b
10) c

#### lulwut

##### New Member
I'm hoping I got all 10 correct (aren't we all):

1)c
2)d
3)c
4)d
5)a
6)b
7)a
8)d
9)b
10)c

#### RealiseNothing

##### what is that?It is Cowpea
I'm hoping I got all 10 correct (aren't we all):

1)c
2)d
3)c
4)d
5)a
6)b
7)a
8)d
9)b
10)c
Fairly sure question 6 is A.

#### Magical Kebab

##### Member
Fairly sure question 6 is A.
I think it is a...
I just though b cos I assumed the whole expression would be divided by 2.

#### lulwut

##### New Member
6a was the general formula one right?

2x should = the general formula i think, so i figured x= (general formula) / 2

Yep 6 would be A

#### Mitsunami

##### Member
1) c
2) d
3) b
4) d
5) a
6) d
7) a
8) d
9) b
10) c

Realized 6 was wrong after the examiners say the exam's over. *sigh*

#### RealiseNothing

##### what is that?It is Cowpea
6a was the general formula one right?

2x should = the general formula i think, so i figured x= (general formula) / 2
The general formula has a $\bg_white 2n\pi$ though, so when you divide by the 2 you just get $\bg_white n\pi$

#### lulwut

##### New Member
Yep 6 would be A
oh wow, just saw the sin-1(a) not a... LOL aw man how did i miss that

#### alexandred

##### New Member
6 is b. Consider the graph of y=sinx; for any given vertical line y=a (|a|<=1) the solutions for intersections are: x = 2kpi + arcsin(a), x = (2k+1)pi - arcsin(a), or equivalently x = kpi + (-1)^k*arcsin(a). Divide this by 2 for 2x

#### RealiseNothing

##### what is that?It is Cowpea
Cambridge 3U year 12, page 33:

"The general solution of $\bg_white \sin(x)=a$ is $\bg_white x=\sin^{-1}(a) + 2n\pi$"

Divide by 2 gets A doesn't it?

Note the (-1)^k

#### lulwut

##### New Member
The general formula has a $\bg_white 2n\pi$ though, so when you divide by the 2 you just get $\bg_white n\pi$
general formula is just pi not 2pi for sin though. and its sin^-1(a) not just a, so sin^-1(a) represents 2x which when divided by 2 is equal to x, which works with the general formula where you have to have the angle at the end. I'm pretty sure it's A) now.

#### Randox

##### Member
qn 2 is b isnt it?

#### lulwut

##### New Member
general formula is just pi not 2pi for sin though. and its sin^-1(a) not just a, so sin^-1(a) represents 2x which when divided by 2 is equal to x, which works with the general formula where you have to have the angle at the end. I'm pretty sure it's A) now.
Im back to thinking it's B) again.. LOL

sin(2x)=a so arcsin(a)=2x

but lets do it in general for sinx first. Sinx=sina so x=a

x=npi+(-1)^n*a

sub in x as 2x and a as arcsin(a)

2x=npi+(-1)^n*arcsin(a)

so x=(npi+(-1)^n*arcsin(a)) / 2 which is answer b)

#### kewon

##### Member
Im back to thinking it's B) again.. LOL

sin(2x)=a so arcsin(a)=2x

but lets do it in general for sinx first. Sinx=sina so x=a

x=npi+(-1)^n*a

sub in x as 2x and a as arcsin(a)

2x=npi+(-1)^n*arcsin(a)

so x=(npi+(-1)^n*arcsin(a)) / 2 which is answer b)
pls be b...
in the test i was thinking dam could be a trick and could be a but i cbf spending more time on it so i just hoped for the best...