The ornamental design for a teachingmaterial, as shown and described.
1.-2. Teaching material
1.1: Front
1.2: Back
1.3: First perspective front
1.4: Second perspective front
1.5: First side
1.6: Second side
1.7: Third side
1.8: Fourth side
1.9: Transition state
2.1: Front view of square state
2.2: Back view of square state
2.3: Perspective front view of square state
2.4: Intermediate state
2.5: Front view of triangle state
2.6: Back view of triangle state
2.7: Perspective front view of triangle state
2.8: Side view of square state
2.9: Second perspective view of triangle state
Design 1: model of a geometrical rearrangement of faces between a square and an equilateral triangle; design 2: model of a geometrical rearrangement of faces between a square and an equilateral triangle.