My first image is a common one of stairs or in my example escalators, I have shown two images here, the first straight on and the second taken from above. I am not sure which one I prefer as the first gives a nice symmetry but the second has more depth by finding that other angle.
My next shot was of an office block with many natural diagonals. I tried to vary the camera as much as possible to find as many possible though in producing this shot.
My third shot was taken in a walkway using the depth of the pillars and the light shining through to make the triangular shapes
And finally this shot was taken on the other side of the walk way by making a triangular shape at the bottom of the image giving it overall more depth.
This exercise has certainly given me insight on how to make an image a little more interesting with a few triangles!