Home > Maths I > Measure and Shape > Angles involved with circles
Maths I
Angles involved with circles
You should be able to answer all of the following questions by looking at the information and diagrams that you have seen in the previous pages:
In this diagram is a diameter and angle .
What is the size of angle ?
is an angle in a semi-circle
so angle
The three angles in the triangle add up to
so angle
In this diagram is the centre of the circle and is a tangent to the circle.
and .
What is the length of ?
is a tangent and is a radius
so angle
We have a right angled triangle and so we can use Pythagoras:
In this diagram is a diameter of the circle and is long. .
Calculate the size of .
is a diameter so we have an angle in a semi-circle and angle .
We have a right angled triangle and so can use Pythagoras.
is not the hypotenuse so:
(to one decimal place)
Impress your mates - how to remember pi to 8 decimal places:
(Don't worry - you don't need to do this in your exam!)
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Video news clip about the advantages for a school in Wales being built with all circular classrooms
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