Question

in this problem 2 questions are arising (1)cos A=taken sqrt why did he taken sqrt here.
(2)nd point he is telling that A is acute on what basis it is acute help me any one ,

Answer 1

see attachment ....

we know that acute angle means angle greater than 0 but less than 90 so wHen angle is acute then cos and sin both are positive..

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hope it will help u