On day 80 of our countdown to exams, we take a look at the topic of Circle theorems. There are 7 key circle theorems you need to be able to recall when faced with questions involving missing angles in circles. In order to secure full marks, you will need to justify your reasoning by stating one or more of the circle theorems (not just the shape) along with other angle facts you know (straight line, triangle, around point etc.).
In today's countdown, we focus on the topic of area and circumference of circles. As with all area formulae, you will need to memorise these for the area and circumference of a circle. Make sure you are dealing with the element of the circle (diameter or radius) before you substitute into the formula. Always double check your calculations to see if your answer is reasonable (circumference is about three times the length of the diameter).
When calculating sector areas and arc lengths remember to work out the proportion of the circle you are dealing with (amount of degrees given over 360). Then it is a case of using the original formulae to calculate your answer.
In this quick countdown, we take a look at all the definitions of the parts of the circle. These will become useful when dealing with circle theorems, area problems involving circles and the equation of a circle. Make sure you are confident in the terms and where they are situated on a circle.
On day 52 of the countdown, we approach the more complex topic of the Equation of a circle. There are a few areas of prior knowledge required to tackle the whole topic completely. You will need to be confident in calculating missing sides using Pythagoras' theorem (to find the radius), calculating the gradient (to find the equation of the radius and then the tangent). Knowledge of perpendicular lines will be required as well as memorising the general rule for the equation of a circle (x2+y2=r2)