Hello, i'm doing some revision and working through the textbook my course follows and have a small problem. The question is an incomplete table of values for sinθ, cosθ, tanθ, [itex]\alpha[/itex] and θ. I have to work out the blanks using what is given. I thought I knew the correct method of doing this, and I got all the answers correct except for the last two lines where I got the value correct, but did not see why I needed to include a ± sign. I'll show what I did for one of the lines, and hopefully someone can see why i'm not realising the values can be negative or positive. 1. The problem statement, all variables and given/known data sinθ = cosθ = tanθ = [itex]\alpha[/itex] = 45° θ = 3. The attempt at a solution I worked out sin, cos and tan for this value of alpha and they were all positive, so I thought I could assume, based on the CAST diagram, that the associated acute angle [itex]\alpha[/itex], must lie in the 1st quadrant. Therefore θ = 45° However, my textbook says all the trig values I obtained can be ± and θ = 45° or 135° What am I missing?