I am not sure if I got it. still can't see the right angle. but you don't need that information. Red points are colinear. Connect the center to big blue point. the centeral angle is 60 degrees, which is already given due to rotation, so: cosine rule: x^2 = 1^2 + 3^2 - 2*1*3*cos(60) x^2 = 1 + 9 - 3 x^2 = 7
ORIGINAL PROBLEM:
This one is more impressive
ReplyDeleteCan someone help me to see why Y=90?
ReplyDeleteThx.
Draw right triangle first, then there can be found some point on little circle which make the bigger triangle equilateral
ReplyDeleteI am not sure if I got it. still can't see the right angle.
ReplyDeletebut you don't need that information. Red points are colinear. Connect the center to big blue point. the centeral angle is 60 degrees, which is already given due to rotation, so:
cosine rule:
x^2 = 1^2 + 3^2 - 2*1*3*cos(60)
x^2 = 1 + 9 - 3
x^2 = 7
-binary