If ` vec R = (vec A = vec B), show that ` R^(2) =A^(2) +B^(20 +2 AB cos theta` wher, ` theta` is the smaller angle between `vec A and vec B`.

If ` vec R = (vec A = vec B), show that ` R^(2) =A^(2) +B^(20 +2 AB co

1.	If ` vec R = (vec A = vec B), show that ` R^(2) =A^(2) +B^(20 +2 AB cos theta` wher, ` theta` is the smaller angle between `vec A and vec B`.
Answer» Given ` vec `R = (vec A + vec B) , Taking dot product of ` R` with itself , we have, ` vec R .vec R = ( vec A+ vec B). ( vec A+ vec B)` or ` R^2 = vec A. vec A + 2 vec A.vec B + vec B. vec B` or ` R^2 = A^2 + 2 AB cos theta + B^2`.

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If ` vec R = (vec A = vec B), show that ` R^(2) =A^(2) +B^(20 +2 AB cos theta` wher, ` theta` is the smaller angle between `vec A and vec B`.

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