I am having trouble on Question 8 found on Page 19 in the textbook on how to construct and obtuse golden triangle over a given base. I understand how to construct the acute golden trinagle but I dont know where to go from there. What do I do to make it an obtuse triangle?
Many ways. However, since you know how to construct an acute golden triangle, I will start from there.
The angles over the base of the obtuse golden triangles are both 36 degrees. That is also the size of the "top" (sharp) angle of any acute triangle. So, construct any acute golden traingle and duplicate the angle of 36 degrees on both sides of the given basis. You get an obtuse golden triangle as required.