CBSE [ Delhi] _XII_Mathematics_2012_Set III

Find ‘ ’ when the projection of  on  is 4 units.

If a line has direction ratios 2, –1, –2, then what are its direction cosines?

Let * be a ‘binary’ operation on N given by a * b = LCM (a, b) for all a,b N .Find 5 * 7.