ANSWER
[tex]d=50.2^o[/tex]EXPLANATION
We are given that d is an acute angle, such that:
[tex]\cos (d)=0.64[/tex]To find the value of d, we have to find the cosine inverse of both sides of the function.
That is:
[tex]\cos ^{-1}(\cos (d))=\cos ^{-1}(0.64)[/tex]Now, simplify:
[tex]\begin{gathered} d=cos^{-1}(0.64) \\ d=50.2^o \end{gathered}[/tex]That is the value of d.
