Question

sin^2 + cos2 =1
explain why ?

Answer 1

Let θ be an angle in standard position with vertex at (0,0). Let (x, y) be a point on the terminal side of θ and let r be the distance from (0,0) to (x,y).

By the distance formula, the distance from (x,y) to (0,0) is r = √[(x-0)2 + (y-0)2] = √[x2+y2]. So, x2 + y2 = r2

By definition, cosθ = x/r and sinθ = y/r

So, cos2θ + sin2 θ = (x/r)2 + (y/r)2 = (x2+y2)/r2 = r2/r2 = 1

Answer 2

Answer:

It is according to the formula sin²ø+cos²ø = 1