Answer
$\theta = 64.3^{\circ}$
Work Step by Step
We can find the area of the triangle:
$A = \frac{\sqrt{3}}{4}~a^2$
$A = \frac{\sqrt{3}}{4}~(0.080~m)^2$
$A = 0.002771~m^2$
We can find the angle $\theta$:
$\phi = B~A~cos~\theta$
$cos~\theta = \frac{\phi}{B~A}$
$\theta = cos^{-1}~(\frac{\phi}{B~A})$
$\theta = cos^{-1}~[~\frac{6.0\times 10^{-6}~Wb}{(5.0\times 10^{-3}~T)~(0.002771~m^2)}~]$
$\theta = 64.3^{\circ}$
