Find cos0 if sin0 =sqrt 2/2 and 0 terminates in quadrant I

Answer 1

In quadrant I

cos θ = √2 / 2

for

θ = π / 4 rad (45°)

sin θ = sin π / 4

sin θ = √2 / 2

tan θ = sin θ / cos θ = ( √2 / 2 ) / ( √2 / 2 ) = 1

Answer 2

sin^2θ + cos^2θ = 1
1/2 + cos^2θ = 1
...

Answer 3

sin A = y/r = sqrt2/2
x^2 + y^2 = r^2
x^2 + 2 = 4
X = sqrt2.
Cos A = x/r = sqrt2/2.