Direction Cosines and Direction Ratios

1.DEFINITION OF D.CS., RELATION BETWEEN D.CS. OF A LINE, CO-ORDINATES OF A
POINT WHEN D.CS. ARE GIVEN AND DIRECTION COSINES OF A LINE JOINING TWO
POINTS.

2. ANGLE BETWEEN TWO LINES WHEN D.CS ARE GIVEN, FINDING THE ANGLE BETWEEN TWO LINES WHEN THEIR D.CS ARE CONNECTED BY EQUATIONS.

3.DEFINITION OF DIRECTION RATIOS, D.RS. OF A LINE JOINING TWO POINTS

4. RELATION BETWEEN D.CS AND D.RS

5. CONDITIONS FOR PARALLEL AND PERPENDICULAR LINES WHEN D.CS/D.RS ARE GIVEN.

6. ANGLE BETWEEN TWO LINES WHEN D.RS ARE GIVEN, FINDING THE ANGLE BETWEEN TWO LINES WHEN THEIR D.RS ARE CONNECTED BY EQUATIONS.