A cylindrical helix is just a spiral on a cylinder, like an ordinary spring or the thread on a bolt. If I turn a left-handed helix over (top to bottom) does it become a right handed helix?
Making Rectangles, Making Squares
Age 11 to 14 Challenge Level:
Imagine you have any number of equilateral triangles all of the same size as well as a large number of $30$ $^\circ$ , $30$ $^\circ$ , $120$ $^\circ$ isosceles triangles with the shorter sides the same length as the equilateral triangles.
Using these triangles how many differently shaped rectangles can you build?
Can you make a square?
The interactivity below may help you with this problem. Click on the green or yellow triangles to get a copy. Drag the triangle by its interior to the required position and drag any vertex to rotate it.
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice.