Answer
$0.967$
Work Step by Step
We know that
$Z=\sqrt{R^2+(\omega C)^{-2}}$
We plug in the known values to obtain:
$Z=\sqrt{(105\Omega)^2+(2\pi(70.0)(82.4))^{-2}}=108.6\Omega$
Now $cos\phi=\frac{R}{Z}$
$cos\phi=\frac{105}{108.6}=0.967$
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