Our angle is written in degree, minutes and seconds format.
Let's say we have the following number on this format
xº y' z''.
To convert this number to decimal, we use the following formula
[tex]x^oy^{\prime}z^{\prime}^{\prime}=(x+\frac{y}{60}+\frac{z}{3,600})^o[/tex]Using this formula in our angle 77º 39', we have
[tex]77^o39^{\prime}=(77+\frac{39}{60}_{})^o=77.65^o[/tex]And this is our answer. Our angle written in decimal form is 77.65º.
