Question 658731
There are 180 degrees in a triangle.  If you want a 1:2:3 ratio, you're talking about 6 equal parts (1+2+3).  So:
180/6 = 30
Each "part" of the ratio is equal to 30 degrees.  So:
1:2:3 = 
30 : 30+30 : 30+30+30 or
30:60:90