calculate the value of (1 sec20¡ã cot20¡ã)(1-cosec20¡ã tan70¡ã)

Answer 1

If you meant

(1+sec20° cot20°)(1-csc20° tan20°)
Then you have

sec20° cot20° = csc20°
csc20° tan20° = sec20°

and the product becomes

(1+csc20°)(1-sec20°)

I don't see anything much else to do.