Question 26351
Sketch the octagon in the circle.  It has eight equal sides.
Join the end points of one of the sides to the center of the
circle to form a triangle.
If you did this for each side you would have eight equal 
angles at the center sharing 360 Degree.
One of those center angles is 360/8=45 degrees
Therefore the other two angles of the triangle you drew
share 180-45 =135 degrees.  Each of them is 135/2=67.5 degrees.
the radii of the circle are 15.8 cm.
Use the Law of Sines to get the following:
15.8/sin 67.5 = x/sin45 where "x" is the length of one side of the octagon.
Using your calculator: x= 11.87
Multiply that by "8" to get the perimeter of the octagon.

2nd problem:
Draw the picture. Then use inverse tangent (35/30) to find the angle
of elevation of the sun.

Cheers,
stan H.