Coordinate geometry describes everything related to the Cartesian plane and is therefore sometimes known as Cartesian geometry. Remember x and y coordinates? The Cartesian plane is the two-dimensional plane formed by the intersection of x and y.
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Jetzt kostenlos anmeldenCoordinate geometry describes everything related to the Cartesian plane and is therefore sometimes known as Cartesian geometry. Remember x and y coordinates? The Cartesian plane is the two-dimensional plane formed by the intersection of x and y.
Coordinate geometry is a very important study as it allows us to develop graphical representations for different things such as parallel and perpendicular lines and curves we couldn't normally graph.
We split Coordinate Geometry into three key sections:
Let's look at these in a bit more detail.
In order to understand coordinate geometry, we will look at straight line graphs in a lot of detail, starting with calculating gradients and intercepts. Then we will move on to parallel and perpendicular lines. Finally, we will start modeling using straight line graphs.
Here's is an example of a question involving straight line graphs. This question will require calculating the gradient.
The amount of money an ice-cream van makes in a day can be modeled as \(y = 5s-12\). Where s is the amount of ice creams sold and y is the amount of money made in pounds.
Find the price of each ice cream.
Calculate the amount of ice cream that needs to be sold so that the ice cream van doesn't make a loss.
SOLUTION: 1. The gradient of this line is the money made from sales. Remember, in a graph, m is the gradient.\(y = mx+c\)Therefore the gradient of this graph is 5. So each sale is £5. To not make a loss \(5s-12 \geq 0\) We can solve this by saying \(5s \geq 12\)
Circles are an important part of coordinate geometry. We can use information about circles along with other theories of coordinate geometry to solve more complicated problems.
Remember, a circle with radius r and center (a, b) has an equation: \((x-a)^2 + (y-b)^2 = r^2\)
A circle has an equation \((x-2)^2 + (y-4)^2 = 25 \qquad (5,8)\)
This is a graphical representation of the circle and perpendicular line:
Parametric equations represent everything in terms of one variable. The variable normally used is t.
This is because there are a lot of more complicated equations where it is better to represent each x and y in terms of the same variable.
Here's an example of a set of parametric equations.
\(x = 2\cos(t); \space y = 2\sin(t)\)This is the parameterization of a circle as:
\(x^2+y^2 = (2\cos(t))^2 + (2\sin(t))^2 = 4 \cos^2(t) + 4 \sin^2(t) = 4(\sin^2(t) + \cos^2(t)) = 4(1)= 4\)
Below is an example of a parametric equations question.
A curve C contains the following parametric equations.
\(x = 4\cos(t+\frac{\pi}{6}); \space y = 2\sin(t)\)Prove that \(x + y = 2\sqrt3 \cos(t)\)
Show that the Cartesian equation of C is \((x+y)^2 +ay^2 = b\) where a and b are constants to be found.
SOLUTION:
Well \(x+y = 4\cos(t+\frac{\pi}{6}) + 2\sin t\).
By addition formula
\(4 \cos(t+\frac{\pi}{6}) = 4\cos(t)\cos(\frac{\pi}{6})-4\sin(t)\sin(\frac{\pi}{6})4\cos(t + \frac{\pi}{6}) = 4\frac{\sqrt3}{2} \cos(t) 2\sin(t) 4\cos(t+\frac{\pi}{6}) = 2\sqrt{3} \cos(t) -2\sin(t)4\cos(t+\frac{\pi}{6}) +2\sin(t) = 2\sqrt3 \cos(t) - 2\sin(t)+2\sin(t) = 2 \sqrt3 \cos(t)\)
2.
\((x+y)^2 = (2\sqrt3 \cos(t))^2 = 12 \cos^2{t}y^2 = 4\sin^2{t} 12\cos^2{t}+4a(\sin^2{t}) = b\)
By \(\sin^2{t} + \cos^2{t} = 1\):
\(12\cos^2{t}+12\sin^2{t} = 124a = 12 \rightarrow a = 3b =12\)
Straight line graphs are decided by a gradient and the y-intercept.
Parallel and perpendicular lines are decided by gradients.
Parallel lines contain the same gradient.
Perpendicular lines have gradients which product -1.
Circle theorems can be used to help find equations of lines on a Cartesian plane.
Coordinate geometry ties together geometrical concepts and rules of lines in Cartesian coordinates.
Parametric Equations involve writing everything in terms of one variable.
Coordinate geometry is the study of the Cartesian plane.
A graph with the equation y=mx+c.
Two lines that contain the same gradient and never meet.
A radius.
What is the radius of a circle?
The distance between the centre of the circle and the circumference.
What is a sector?
An area bordered by two radii.
What is a chord?
A line that goes from one side of circumference to the other without going through the centre.
What is a segment?
An area bordered by a chord or a circumference.
What is a tangent?
A line outside of the circle that touches the circumference of a circle at one point.
What is an arc?
A section of the circumference.
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