The quartz is more resistant to abrasion and chemically more resistant than the feldspar. The result is that the quartz remains in the stream but the feldspar breaks down to clay or is dissolved.
(this is from coursehero.com)
Bands of soft rocks like clay and sand are very weak in which they can be eroded very quickly. Since cliff and coastline doesn't erode at the the same pace, an inlet of the sea to where the land curves inward forming a bay. Once soft rocks are eroded inward, the hard rocks are able to stick to the sea to form a headland
Angles in a triangle add to 180 so
55 + 23 = 78 so 180 - 78 = 102 so the other angle in the triangle would be 102 degrees
