# Thread: Points on a circle.3

1. ## Points on a circle.3

In the diagram attached a is the centre ogf the circle (O doesn't work in paint).
P,Q,R and S are points on the circle
Angle ROP = 110
Calculate the angle RSP

I Don't know how to prove it is a parallelogram (if it is (although I suspect it is)), I need names of laws and if there are specific names given to various angles (not like obtuse or acute but things like RSP is the intercept angle, although I know it's not but I don't know what the intercept angle is)

This is all GCSE standard, please do not venture further.

2. Originally Posted by Mukilab
This is all GCSE standard, please do not venture further.
WHAT does that mean?

Is angle PQR = 35 ?

3. No, 55, apologies for that.

I mean this is for my GCSEs and because I have never taken any maths classes I have to learn this all by myself within an incredibly small amount of time so I do not want people to elaborate because I will simply not remember the equations.

GCSEs are national exams in England.

4. Originally Posted by Mukilab
In the diagram attached a is the centre ogf the circle (O doesn't work in paint).
P,Q,R and S are points on the circle
Angle ROP = 110
Calculate the angle RSP
Hi Mukilab,

Your drawing leaves something to be desired. If you're using Paint, take your time.

If angle ROP = 110, and if it is a central angle, then arc RSP is also 110 degrees.

That leaves 360 - 110 = 250 degrees for arc RQP (the rest of the circle).

Angle RSP is an inscribed angle that intercepts this arc, so
it is one-half its measure.

That makes Angle RSP = 1/2 (250) or 125 degrees.

I don't know what a parallelogram has to do with anything.