`(1+sec20^(@)+cot70^(@))(1-"co s ec"20^(@)+tan70^(@))` is equal to

Options

A. 0
B. 1
C. 2
D. 3

Answer

c

Explanation

`(1+sec20+cot70)(1-co s ec20^(@)+tan70^(@))`
`[1+sec20+tan20](1-co s ec20+tan20)`
put `45^(@)` in place of ` 20^(@)`
`(1+sec45^(@)+tan45)(1-co s ec45^(@)+cot45^(@))`
` (1+sqrt(2)+1)(1-sqrt(2)+1)`
`(2+sqrt(2))(2-sqrt(2))=2`