Question

Triangle XYZ is reflected across the y-axis to create triangle PQR (not shown).

What is the measure, in degrees, of angle R

Answer 1

The measure of ∠R = 60°

Explanation:

The given parameters are;

Triangle XYZ is reflected across the y-axis to create triangle PQR

The measure of ∠Y = 30°

Triangle XYZ = A right triangle

The measure of ∠X = 90°

Where we have;

The image of the preimage of vertex X = P

The image of the preimage of vertex Y = Q

The image of the preimage of vertex Z = R

Therefore, given that a reflection is a rigid transformation, we have;

The measure of ∠X = The measure of ∠P

The measure of ∠Y = The measure of ∠Q

The measure of ∠Z = The measure of ∠R

Given that the measure of ∠Y = 30° and the measure of ∠X = 90°

∠X +∠Y + ∠Z = 180° (angle summation of a triangle property

∴ The measure of ∠Z = 180° - (∠X + ∠Y) = 180° - (90° + 30°) = 60°

Therefore;

The measure of ∠Z = 60° = The measure of ∠R

The measure of ∠R = 60°.