Q: Geometry and Angles
Ray RY bisects angle NRT
Measure of angle NRY = 2x² + 6x
Measure of angle YRT = 10x + 6
Find x and the measure of angle YRT
A: Ahhh, fun to answer without a picture. But, we can do it. We have an angle that is bisecting. Bisected means cut in half. Therefore, angle NRY = angle YRT:
Mathematically: 2x² + 6x = 10x + 6
Now, time to solve! Since I see an “x²”, I think to myself that we must factor this. First step to factoring? Set the equation equal to zero:
2x² + 6x = 10x + 6
2x² + 6x – 10x = 6
2x² + 6x – 10x – 6 = 0
2x² – 4x – 6 = 0
Now, this is a quadratic that needs solving. We can either solve using the quadratic equation or by factoring. Let’s factor (View Factoring 101 for the basics of factoring):
2x² – 4x – 6 = 0
(2x )(x ) = 0
(2x + )(x – ) = 0 [I know there is a – and a + because the two numbers must multiple to give -6… And, a – times a + equals a -, right? However, I do not know that the + goes with the 2x and the – goes with the x… This is just my best guess to start. Factoring can be treated as a guessing game – if you use guess and check, you get better at it with time.]
(2x + 2)(x – 3) = 0
So,
(2x + 2) = 0 or (x – 3) = 0
x = -1 or 3
We have two potential answers. Take note, if x=-1, then we have:
Angle NRY = 2x² + 6x = 2(-1)² + 6(-1) = 2 – 6 = -4
An angle cannot be negative, therefore x cannot be -1.
Therefore, x must equal 3:
Angle YRT = 10x + 6
So, if x = 3:
Angle YRT = 10(3) + 6 = 30 + 6 = 36.