If tan A=, then sin A. cos A=.


Given:

And we know,


So


perpendicular = 3k and base = 4k


By Pythagoras theorem, (hypotenuse)2 = (perpendicular)2 + (base)2


(hypotenuse)2 = (3k)2+ (4k)2 = 9k2+16k2 = 25k2


hypotenuse = 5k


[ (hypotenuse)2 = 25k2 hypotenuse = (25k2) = 5k)


Thus, sin A and cos A can be found out.




Multiplying sin A and cos A,



Hence, proved.


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