If a line joining two points A (2, 0) and B (3, 1) is rotated about A in anticlockwise direction throughan angle 15º, then equation of the line in the new position is

Slope of AB =1−03−2=1⇒ ∠BAX=45∘ (Ref. Fig. 16.18) If AC is the new position of the line AB then  ∠CAX=45∘+ 15º = 60ºand thus its equation isy=tan⁡60∘(x−2)y=3(x−2) ⇒ 3x−y=23