Turning triangles between rectilinear and curvilinear form
Squaring curved-sided triangles by removing and restoring circular portions
A geometry page of quadrature exercises on curved-sided triangles. Leonardo makes a rectilinear triangle equal to a triangle of two curved sides by removing portion b from triangle a b and giving it back at c, so the same two parts recompose as a curvilinear triangle a c. He applies the same method to square triangle f into triangle n m (shown by figure g), notes that the bisangular falcata is squared as previously drawn, and remarks that the falcate pyramid here is built from circles double one another.
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Making a rectilinear triangle equal to a curved-sided one
Removing portion b from triangle a b leaves a alone; giving b back at site c rejoins the same two parts that composed the rectilinear triangle, but now they form a curvilinear triangle a c, equal in quantity to the original.
Squaring triangle f into triangle n m
By the same method Leonardo squares the triangle f, producing the triangle n m as the third figure g demonstrates. The bisangular sickle (falcata) figure is squared in the manner drawn above, and the falcate pyramid here is made of circles double one to the other.