Demonstrating Sphere Volume Formula by Dan Dale
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This example dynamically demonstrates how to derive the volume formula of a sphere by rotating a cylinder and a cone. Key math concepts include volume calculation, solids of revolution, integral concepts, and geometric transformations. GeoGebra commands and objects used in construction are Circle, Cylinder, Cone, Rotate, and Surface. Suitable for high school solid geometry teaching to help students visually understand the origin of the sphere's volume formula.
GeoGebra Commands & Parameters
Circle(A, 1) → cCircle(B, 1) → dPoint(c) → CSphere(A, C) → aCylinder(B, D, 1) → b, e, f, gCone(D, B, 1) → h, k, iSegment(E, E + (0, 0, 1)) → jPoint(j) → FOrthogonalPlane(F, j) → lIntersectPath(l, a) → pIntersectPath(l, h) → qIntersectPath(l, b) → rPoint(q) → HIntersect(Ray[G, H], r) → I,Rotate(H, α, G) → H'Rotate(I, α, G) → I'Polygon(H, H', I', I) → poly1, h_1, h', i', i_1Sequence(Rotate[poly1, (k * α), G], k, 0, n) → list1Intersect(Ray[J, J + (1, 0, 0)], p) → K,Segment(A, J) → sSegment(J, K) → tSegment(K, A) → a_1Intersect(Ray[G, G + (1, 0, 0)], q) → L, MSegment(B, G) → b_1Segment(G, L) → c_1Circle(s, C) → d_1Angle(A, J, K) → βAngle(B, G, L) → γCircle(B, 1, Segment[B, B + (0, 0, 1)]) → e_1Surface((sqrt(1 - h^(2)) * cos(θ)) + x(A), (sqrt(1 - h^(2)) * sin(θ)) + y(A), h, θ, 0, 6.28319, h, 0, 1) → o