Approach a point from the left and right, then watch the function values move toward a common value — or fail to do so.
Allowed: sin, cos, tan, sqrt, log, exp, abs, pi, e. Piecewise: x<1 ? 2 : 5
x-min
x-max
f(x)left: x = a − hright: x = a + hx = a
Left-side value
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Right-side value
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Function value at a
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Observation
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Classroom idea: Pause the marker and ask students: "Do the left-hand and right-hand y-values approach the same number?" If yes, discuss the limit. If not, ask whether the problem is a jump, asymptote, or oscillation.