Misc: What zodiacal sign is represented by a bull?

Questions

[science and technology] in dyeing what is the name given to the substance used for fixing the colour?

[science and technology] what is the name given given to the lowest temperature theoretically possible?

[science and technology] what is the mathematical term used to describe the shape of a cell in a honeycomb?

[science and technology] how many degrees are there in a circle?

[science and technology] what is the name given to the green pigment in plants?