I'm guessing that you don't really want the formulas. I think what you actually want
is the definitions of those functions of an acute angle when it's in a right triangle.
Cosine = (adjacent side) / (hypotenuse)
Tangent = (opposite side) / (adjacent side)
Sine = (opposite side) / (hypotenuse)
Tell me if I'm wrong, and I'll find some formulas for you.
Regular price: $419
Sale price: (1-0.205)($419) = $333.11
The bike will cost $333.11 before tax. You haven't shared the tax rate, but I can at least tell you that the cost of the bike after tax will be
(1.00 + rate as a decimal fraction)*$333.11.
Example: If the tax rate is 7.5%, then the bike will cost (1.00+0.075)*($333.11).
Think it's B or A if they want it simplified.
