Functions — Syllabus
ICSE · Class 12 · Mathematics
What Functions covers in ICSE Class 12 Mathematics: 4 topics, for the 2026-27 session. Part of the ICSE Class 12 Mathematics syllabus.
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Topics in Functions
1. Basic idea of a function
- A relation from a set A to a set B is a function only if every element of A has exactly one image in B.
- A function can be written as f: A → B.
- Domain is the set A, co-domain is the set B, and range is the set of all images of elements of A.
2. Standard real functions and their graphs
- Constant function: f(x)=k for all x∈R; domain R, range {k}; graph is a line parallel to the x-axis.
- Identity function: f(x)=x for all x∈R; domain R, range R; graph passes through the origin at 45° to the x-axis.
- Polynomial function: f(x)=a0+a1x+...+anx^n for all x∈R, with real coefficients and non-negative integer n; domain R, range subset of R.
3. Domain and range of real functions
- A real function must take real values for every input in its domain.
- For rational functions, denominators must not be zero.
- For square root expressions, the quantity under the square root must be non-negative.
4. Graphical tests
- Graphical Test for Function: If any straight line parallel to the y-axis does not cut the curve at more than one point, then the curve represents a function.
- Graphical Test for One-one Function: If any straight line parallel to the x-axis does not cut the graph of a function at more than one point, then the curve represents a one-one function.
- The vertical line test checks whether a graph represents a function.
Key Concepts
Central concept: Functions as a special type of relation between two sets
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