Question

two vector A and B are such that vector A + vector B equal to vector C and a square + b square + equal to C square find the angle theta between the two vector

Answer 1

the vectors are a and b ,if we add,the square of magnitude of resultant vector is ..
c^2=a^2+b^2+2abcos theta.
where theta is the angle between the vectors.
but a^2+b^2=c^2.
so c^2=c^2+2abcos theta.
or 2abcos theta=0
cos theta=0
theta=90°