If the line segment joining the points A...

If the line segment joining the points A(a,b) and B(c,d) subtends an angle `theta` at the
origin, then `costheta` is equal to

A

(a) `(ab+cd)/(sqrt((a^(2)+b^(2))(c^(2)+d^(2))))`

B

(b) `(ac+bd)/(sqrt((a^(2)+b^(2))(c^(2)+d^(2))))`

C

(c) `(ac-bd)/(sqrt((a^(2)+b^(2))(c^(2)+d^(2))))`

D

(d) `(ad+bc)/(sqrt((a^(2)+c^(2))(b^(2)+d^(2))))`

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The correct Answer is:

B

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