All circular triangles are plane figures.
All circular triangles are three-sided figures.
Therefore, some three-sided figures are plane figures.

Use Venn diagrams to determine whether the following standard-form categorical syllogisms are valid from the Boolean standpoint, valid from the Aristotelian standpoint, or invalid. Then, identify the mood and figure, and cross-check your answers with the tables of valid syllogisms found in Section 5.1.

Tables From Section 5.1: