Angle ABC is formed by segments AB and BC on the coordinate grid:

Question

spring98 · Answer

https://cv-kettle-falls.brainhoney.com/Resource/30603643,0/Assets/75195_53df876f/02_04_07.gif

spring98 · Answer

Angle ABC is rotated 90 degrees counterclockwise about the origin to form angle A'B'C'. Which statement shows the measure of angle A'B'C'? 

 	
	A. m∠A'B'C' = 90 degrees
	B. m∠A'B'C' = 180 degrees
	C. m∠A'B'C' = m∠ABC
	D. m∠A'B'C' = 2 ×m∠ABC

spring98 · Answer

@Michele_Laino  can you help me?

michele_laino · Answer

a rotation around the origin of the whole cartesian plane doesn't affect the measure of the amplitude of an angle

spring98 · Answer

so how do i find my answer?

michele_laino · Answer

for example, after rotation, we have:
point C goes to C'=(-2,3)
point B goes to B'=(-3,5)
point A goes to A'=(-4,3)

michele_laino · Answer

try to draw those new points A', B', and C' please

spring98 · Answer

okay hold on

spring98 · Answer

ok i did it on geogebra  so what would the answer be @welshfella