If a+b+c=0 and |a|=3, |b|=5, |c|=7, find the angle between a and b.

Asked by sunil2791 | 24th Nov, 2017, 07:20: PM

Expert Answer:

begin mathsize 16px style straight a with rightwards harpoon with barb upwards on top plus straight b with rightwards harpoon with barb upwards on top plus straight c with rightwards harpoon with barb upwards on top equals 0
straight a with rightwards harpoon with barb upwards on top plus straight b with rightwards harpoon with barb upwards on top equals negative straight c with rightwards harpoon with barb upwards on top
squaring space on space both space sides comma
open parentheses straight a with rightwards harpoon with barb upwards on top plus straight b with rightwards harpoon with barb upwards on top close parentheses squared equals straight c with rightwards harpoon with barb upwards on top squared
straight a with rightwards harpoon with barb upwards on top squared plus straight b with rightwards harpoon with barb upwards on top squared plus 2 straight a with bar on top times straight b with rightwards harpoon with barb upwards on top equals straight c with rightwards harpoon with barb upwards on top squared
straight a with rightwards harpoon with barb upwards on top squared plus straight b with rightwards harpoon with barb upwards on top squared plus 2 open vertical bar straight a with rightwards harpoon with barb upwards on top close vertical bar stack open vertical bar straight b close vertical bar with rightwards harpoon with barb upwards on top cosθ equals straight c with rightwards harpoon with barb upwards on top squared
Put space the space values space given space in space the space question space you space will space get space angle space between space straight a with rightwards harpoon with barb upwards on top space and space straight b with rightwards harpoon with barb upwards on top.

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Answered by Sneha shidid | 28th Nov, 2017, 05:24: PM