12. x➝0⁻: f(x)➝0; x➝0⁺: f(x)➝sin(x)➝0; x➝0, f(x)➝0
x➝1⁻ and x➝1⁺ and x➝1, f(x)➝sin(1)
x➝2⁻: f(x)➝sin(2); x➝2⁺: f(x)➝1; x➝2, limit undefined for f(x) for x➝2 because the other two limits are not equal.
13. x➝1⁻, x➝1⁺ and x➝1, g(x)➝1
x➝2⁻: g(x)➝1; x➝2⁺: g(x)➝4; x➝2: g(x) undefined
x➝4⁻: g(x)➝2; x➝4⁺: g(x)➝2; x➝4; g(x)➝2
x➝5⁻, x➝5⁺ and x➝5: g(x)➝1