Find the values of u for which the angle between the vectors a=2u^2i+4uj+k and b=7i-2j+uk is obtuse.

Asked by sunil2791 | 21st Nov, 2017, 06:13: PM

Expert Answer:

Angle between two vectors is given by
begin mathsize 16px style cosθ equals open vertical bar fraction numerator straight a with rightwards harpoon with barb upwards on top times straight b with rightwards harpoon with barb upwards on top over denominator open vertical bar straight a with rightwards harpoon with barb upwards on top close vertical bar squared open vertical bar straight b with rightwards harpoon with barb upwards on top close vertical bar squared end fraction close vertical bar
Here space angle space will space be space obtuse space if space and space only space if space straight a with rightwards harpoon with barb upwards on top times straight b with rightwards harpoon with barb upwards on top space is space negative.
Use space this space condition space and space get space value space of space straight u end style

Answered by Sneha shidid | 29th Nov, 2017, 12:41: PM