Using a double-angle or half-angle formula to write the expression as a trigonometric function of one angle:

(a) If cos⁡2(27∘)−sin⁡2(27∘)=\displaystyle {{\cos}^{{2}}{\left({27}^{\circ}\right)}}-{{\sin}^{{2}}{\left({27}^{\circ}\right)}}=  

(b) If cos⁡2(7x)−sin⁡2(7x)=\displaystyle {{\cos}^{{2}}{\left({7}{x}\right)}}-{{\sin}^{{2}}{\left({7}{x}\right)}}=   .

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