your expression is meaningless, CLOWN!

Assuming there's a sin in the beginning of all that like sin(70°)cos(10°)−cos(70°)sin(10°)

Recall sin(x-y) = sinx*cosy - cosx*siny.

Fits.

sin(70-10°) = sin(70°)cos(10°)−cos(70°)sin(10°) = sin(60°) = sqrt3 / 2

I presume you mean: sin(70)cos(10) - cos(70)sin(10)

Learn your trig identities and rules:

sin(a - b) = sin(a)cos(b) - sin(b)cos(a)

sin(70 - 10) =>

sin(60)

You should know sin(60)