All SAT Mathematics Resources
Example Questions
Example Question #8 : Using Radians
radians is equivalent to how many degrees?
1 radian is equal to degrees. Using this conversion factor,
.
Example Question #9 : Using Radians
Simplify your answer.
Convert to radians:
We know that:
Radians
since the giving angle was in degrees then we multiply
Example Question #10 : Using Radians
Give your answer in terms of .
Convert to radians:
To convert degrees to radians, we need to multiply the given degree by .
To simplify, we get:
Example Question #1 : Applying The Equation Of A Circle
What is the equation for a circle of radius 12, centered at the intersection of the two lines:
and
?
None of the other answers
To begin, let us determine the point of intersection of these two lines by setting the equations equal to each other:
To find the y-coordinate, substitute into one of the equations. Let's use :
The center of our circle is therefore: (–41, –161).
Now, recall that the general form for a circle with center at is:
For our data, this means that our equation is:
or
Example Question #2 : Applying The Equation Of A Circle
What is the radius of a circle with the equation ?
We need to expand this equation to and then complete the square.
This brings us to .
We simplify this to .
Thus the radius is 7.
Example Question #1 : Applying The Equation Of A Circle
A circle has its origin at . The point is on the edge of the circle. What is the radius of the circle?
There is not enough information to answer this question.
The radius of the circle is equal to the hypotenuse of a right triangle with sides of lengths 5 and 7.
This radical cannot be reduced further.
Example Question #3 : Applying The Equation Of A Circle
A circle with a radius of five is centered at the origin. A point on the circumference of the circle has an x-coordinate of two and a positive y-coordinate. What is the value of the y-coordinate?
Recall that the general form of the equation of a circle centered at the origin is:
We know that the radius of our circle is five. Therefore, we know that the equation for our circle is:
Now, the question asks for the positive y-coordinate when . To solve this, simply plugin for :
Since our answer will be positive, it must be .
Example Question #2 : Applying The Equation Of A Circle
The following circle is moved spaces to the left. Where is its new center located?
Remember that the general equation for a circle with center and radius is .
With that in mind, our original center is at .
If we move the center units to the left, that means that we are subtracting from our given coordinates.
Therefore, our new center is .
Example Question #4 : Applying The Equation Of A Circle
A square on the coordinate plane has vertices at the points with coordinates , , , and . Give the equation of the circle that circumscribes the square.
The equation of the circle on the coordinate plane with radius and center is
The figure referenced is below:
The center of the circle is at the point of intersection of the diagonals, which, as is the case with any rectangle, bisect each other. Therefore, looking at the diagonal with endpoints and , we can set in the midpoint formula:
and
The center of the circumscribing circle is therefore .
The radius of the circumscribing circle is the distance from this point to any point on the circle. The distance formula can be used here:
Since we are actually trying to find , we will use the form
Choosing the radius with endpoints and , we set and substitute:
Setting and and substituting in the circle equation:
, the correct response.
Example Question #5 : Applying The Equation Of A Circle
The above figure shows a circle on the coordinate axes with its center at the origin. has length .
Give the equation of the circle.
A arc of a circle represents of the circle, so the length of the arc is three-eighths its circumference. Set up the equation and solve for :
The equation of a circle on the coordinate plane is
,
where are the coordinates of the center and is the radius.
The radius of a circle can be determined by dividing its circumference by , so
The center of the circle is , so . Substituting 0, 0, and 8 for , , and , respectively, the equation of the circle becomes
,
or
.
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