“3. (+) Use special triangles to determine geometrically the values of sine, cosine, tangent for π/3, π/4 and π/6, and use the unit circle to express the values of sine, cosine, and tangent for π–x, π+x, and 2π–x in terms of their values for x, where x is any real number.”

Was tau taken into consideration while forming the standards? It really is a completely superior notation to the use of π and if anybody was really going to be able to put some muscle behind the introduction of tau notation, it would be CCSS.

http://tauday.com/tau-manifesto

I understand that the standards don’t require using pi only to the exclusion of tau, but perhaps even a mention in the progressions could get more people moving in the right direction.