If `s e c4A=cos e c(A-20^@)` , where 4A is an acute angle, find the value of A.

Explanation

Therefore,:

`sin (A-20^{circ})=cos (4 A) `

`sin (A-20^{circ})=sin (90^{circ}-4 A)`


Hence,


`A-20^{circ}=90^{circ}-4 A `

`5 A=110^{circ} `

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