Year 12s: what will be the first way you research your future options? >>

Radians

I'm struggling with this question, I've done part A, I don't know where to start with B.

https://gyazo.com/20f0a063eab9fa1189aded7966265993

Trig - SohCahToa

SohCahToa?

Help?

Original post by Naruke

Help?

if you rearrange RsinΘ = r ( 1 + sinΘ )

to make sinΘ the subject it comes out quickly

Reply 5

Naruke

Original post by the bear

if you rearrange RsinΘ = r ( 1 + sinΘ )

to make sinΘ the subject it comes out quickly

I did and I got:

Sin \theta = \frac {r+rSin \theta}{R}

But I don't how understand how they got that, because I've used both sine rule & ratio but I don't get that :/

Reply 6

Francesca Meng

Original post by Naruke

I'm struggling with this question, I've done part A, I don't know where to start with B.

https://gyazo.com/20f0a063eab9fa1189aded7966265993

CE=OCsin?
r=[R-r]sin?
r+rsin?=Rsin?
Rsin?=r[1+sin?]

Sorry, ?=theta

Reply 7

the bear

Original post by Naruke

I did and I got:

Sin \theta = \frac {r+rSin \theta}{R}

But I don't how understand how they got that, because I've used both sine rule & ratio but I don't get that :/

you need to get all the sinΘ together on the same side...

Reply 8

Naruke

Original post by the bear

you need to get all the sinΘ together on the same side...

I don't understand what you talking about :colondollar:

but, I've thought of something... would this be ok?

CE is perpendicular to OB therefore OEC will be

90^o

As OT bisects O, COE will be

\theta

so,

Sin \theta = \frac {r}{R-r}

(R-r)Sin \theta = r

RSin \theta - rSin \theta = r

RSin \theta = r + rSin \theta

RSin \theta = r(1 + Sin \theta)

(edited 8 years ago)

Reply 9

Francesca Meng

Original post by Naruke

I don't understand what you talking about :colondollar:

but, I've thought of something... would this be ok?

CE is perpendicular to OB therefore OEC will be

90^o

As OT bisects O, COE will be

\theta

so,

Sin \theta = \frac {r}{R-r}

(R-r)Sin \theta = r

RSin \theta - rSin \theta = r

RSin \theta = r + rSin \theta

RSin \theta = r(1 + Sin \theta)

That's fine :smile:

Reply 10

Naruke

Original post by Francesca Meng

That's fine :smile:

Thanks

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