Question

-2cos70 degrees . cosec20 degrees = 0​

Answer 1

the answer of the question is in the above photo

Answer 2

convert sin 70° in terms of cos 20° so that it gets cancled.(sin(90-¤)=cos¤)-------------i

similarly convert cosec 20°in terms of sec70° so that it gets cancled.(cosec(90-¤)=sec¤)

similarly convert cosec20° in terms of 1/sin20° and then covert sin20° In terms of cos 70° by using same formula which is applied in case i

this will give u

1+1-2
2-2
0
hence =RHS hence proof

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