Using a double-angle or half-angle formula to simplify the given expressions.

(a) If cos⁡2(38∘)−sin⁡2(38∘)=cos⁡(A∘),\displaystyle {{\cos}^{{2}}{\left({38}^{\circ}\right)}}-{{\sin}^{{2}}{\left({38}^{\circ}\right)}}={\cos{{\left({A}^{\circ}\right)}}}, then

A=\displaystyle {A}=   degrees

(b) If cos⁡2(9x)−sin⁡2(9x)=cos⁡(B),\displaystyle {{\cos}^{{2}}{\left({9}{x}\right)}}-{{\sin}^{{2}}{\left({9}{x}\right)}}={\cos{{\left({B}\right)}}}, then

B=\displaystyle {B}=   .

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