Examine the following three lines written in general form:
L1:2x−5y+3=0,L2:10x−25y−4=0,L3:5x+2y−11=0.
(i) Identify all pairs of these lines that are parallel, giving reasons.
(ii) Identify all pairs of these lines that are perpendicular, giving reasons.
(iii) For any pair of lines among L1,L2, and L3 that are neither parallel nor perpendicular, calculate the acute angle between them.