Hi,
Let assume a the width and b the length of the rectangular area.
A sinusoid is cyclical and has a period or frequency.
y = sin x is a sinusoid, with a period of 2π.
y = √x is not a sinusoid.
y = cos x is a sinusoid with a period of 2π.
Answer: y = √x is not a sinusoid.
Measure of z is 116°.The measure of y is 48°.Hope this helps.
Calculate area of the white region inside circle.
Area of the two white triangles in top left and bottom right:

Area of the two white quarter circles in the bottom left and top right:

Total area of unshaded white region inside circle:

Area of entire circle including the white and shaded regions

Area of shaded region is area of entire circle - area of unshaded white region

The measure of the angle formed by 2 chords that intersect inside the circle is 1/2 the sum of the chords' intercepted arcs.
m∠RST = (143+33)/2 = 176/2 = 88°