Two equal vectors have thier resultant equal to either of them.At what angle are they inclined to each other?

Asked by satyapaldpr | 6th Aug, 2015, 08:01: PM

Expert Answer:

begin mathsize 14px style Let space the space two space vectors space be space straight P with rightwards arrow on top space and space straight Q with rightwards arrow on top space and space resultant space be space straight R with rightwards arrow on top According space to space the space given space condition comma open vertical bar straight P with bar on top close vertical bar equals open vertical bar straight Q with bar on top close vertical bar equals open vertical bar straight R with rightwards arrow on top close vertical bar equals open vertical bar straight S with rightwards arrow on top close vertical bar straight R equals square root of straight P squared plus straight Q squared plus 2 space PQ space cos space straight theta end root straight S equals square root of straight S squared plus straight S squared plus 2 space straight S cross times straight S space cos space straight theta end root straight S equals square root of 2 straight S squared plus 2 straight S squared space cos space straight theta end root straight S equals square root of 2 space straight S space square root of 1 plus cos space straight theta end root straight S squared equals 2 straight S squared left parenthesis 1 plus cos space straight theta right parenthesis left parenthesis 1 plus cos space right parenthesis equals 1 half cos space straight theta equals 1 half minus 1 cos space straight theta equals negative 1 half straight theta equals cos to the power of negative 1 end exponent open parentheses negative 1 half close parentheses rightwards double arrow straight theta equals 120 degree end style

Answered by Faiza Lambe | 7th Aug, 2015, 08:23: AM