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Coodinate geo question!! CIE

Hello, I don't get the first part of this question, it tells you the area of the triangle and the segment are equal.
https://gyazo.com/c18d05c07dbdfba700e1eee58affc014

So i guess:

Area of triangle:
0.5*a*b*sinc
0.5*r*r*sinθ
0.5*r^2sinθ

Then segment is sector area - triangle so:
(0.5r^2θ) - (0.5*r^2sinθ)

And are of triangle = segment so:
0.5*r^2sinθ = (0.5r^2θ) - (0.5*r^2sinθ)

But I don't get how or where would the P come from.

Is my working out up till now correct? Or have I misread the question.
Original post by Jian17
Hello, I don't get the first part of this question, it tells you the area of the triangle and the segment are equal.
https://gyazo.com/c18d05c07dbdfba700e1eee58affc014

So i guess:

Area of triangle:
0.5*a*b*sinc
0.5*r*r*sinθ
0.5*r^2sinθ

Then segment is sector area - triangle so:
(0.5r^2θ) - (0.5*r^2sinθ)

And are of triangle = segment so:
0.5*r^2sinθ = (0.5r^2θ) - (0.5*r^2sinθ)

But I don't get how or where would the P come from.

Is my working out up till now correct? Or have I misread the question.


You need so simplify and rearrange your equation into the form:

θ=something ×sinθ\theta = \text{something }\times \sin\theta

And whatever the "something" is, is the p.
Reply 2
how do I finish this( if it's right) image-065163a5-8dfd-4510-ba3a-7c29998d1970645320060-compressed.jpg.jpeg
Reply 3
Looks good, the question wants you to find p so mention the value of p.

Also, just for future reference, you could also say:

(Area of traiangle) = (1/2)(Area of sector), (as the questions states areas of triangle and the segment are equal).

Therefore:

(1/2)r(rsin(θ))=(1/2)[(1/2)θr2]. (1/2)r(r \sin(\theta)) = (1/2) \left[ (1/2) \theta r^{2} \right].

Simplifying to:

(1/2)r2sin(θ)=(1/4)r2θ(1/2) r^{2} \sin(\theta) = (1/4) r^{2} \theta .
(edited 6 years ago)
Reply 4
Original post by Jian17
Hello, I don't get the first part of this question, it tells you the area of the triangle and the segment are equal.
https://gyazo.com/c18d05c07dbdfba700e1eee58affc014

So i guess:

Area of triangle:
0.5*a*b*sinc
0.5*r*r*sinθ
0.5*r^2sinθ

Then segment is sector area - triangle so:
(0.5r^2θ) - (0.5*r^2sinθ)

And are of triangle = segment so:
0.5*r^2sinθ = (0.5r^2θ) - (0.5*r^2sinθ)

But I don't get how or where would the P come from.

Is my working out up till now correct? Or have I misread the question.


you were right on the first bit.

Try to work out the area of the triangle in terms of r and theta and the area of the segment in terms fo r and theta.

You should get an equation with just r and theta, and if u rearrange and simplify it, the r's should be cancelled out then you would have just theta and some numbers. the theta will appear in two areas and try to rearrange to make theta the subject.

Because i'm typing, x = theta

therefore
Area of triangle = sinxr^2/2
then use this to work out the area of the segment and make the area of the triangle and the segment equal each other.

I've got the answer in my hands right now. Tell me if you are stuck again.
Original post by Jian17
how do I finish this( if it's right)


So, θ=2sinθ\theta = 2 \sin\theta

Compare this with θ=psinθ\theta = p\sin\theta

So, p=2
Reply 6
Original post by ghostwalker
So, θ=2sinθ\theta = 2 \sin\theta

Compare this with θ=psinθ\theta = p\sin\theta

So, p=2


Damn, I had it right in front of my eyes :angry:.

Thanks!
Reply 7
Original post by simon0
Looks good, the question wants you to find p so mention the value of p.

Also, just for future reference, you could also say:

(Area of traiangle) = (1/2)(Area of sector).

Therefore:

(1/2)r(rsin(θ))=(1/2)[(1/2)θr2]. (1/2)r(r \sin(\theta)) = (1/2) \left[ (1/2) \theta r^{2} \right].

Simplifying to:

(1/2)r2sin(θ)=(1/4)r2θ(1/2) r^{2} \sin(\theta) = (1/4) r^{2} \theta .


Does that can be used in all cases?

Is it always area of triangle = 0.5*area of sector?

Not sure about it :s-smilie:
Reply 8
Original post by Jian17
Does that can be used in all cases?

Is it always area of triangle = 0.5*area of sector?

Not sure about it :s-smilie:


The questions states the areas of triangle AOB and segment AXB are equal.

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