Using integration find the area of region bounded by the ellipse `x^2/16 + y^2/25 = 1`

Using integration find the area of region bounded by the ellipse x^2/16 + y^2/9 = 1

Using integration find the area of region bounded by the ellipse x^2/25 + y^2/16 = 1

Find the area of region bounded by the ellipse x^2/4 + y^2/9 = 1

Using integration, find the area of the region bounded by the circle x^2 + y^2 = 16 and line y=x in the first quadrant.