For a general angle you couldn't calculate the trigonometric values in your head!
However, there are some that are worth remembering.
sin(30°) = 1/2 cos(30°) = sqrt(3)/2
sin(60°) = sqrt(3)/2 sin(60°) = 1/2
sin(45°) = cos(45°) = 1/sqrt(2)
You can find the corresponding tan by dividing sin by cos (i.e. tan = sin/cos)
.
