Hyperbolic Functions & Graphs
What are the definitions of the hyperbolic functions?
- Hyperbolic sine
-
- This can be pronounced "shine" or "sinch"
- Hyperbolic cosine
-
- This can be pronounced "cosh"
- Hyperbolic tangent
-
- This can be pronounced "than" or "tanch"
What are the graphs of the hyperbolic functions and their key features?
-
- Domain:
- Range:
- Non-stationary point of inflection at (0, 0)
- Its shape is similar to the graph of
-
- Domain:
- Range:
- Global minimum point at (0, 1)
- Its shape is similar to the graph of
-
- Domain:
- Range:
- Non-stationary point of inflection at (0, 0)
- Asymptotes at y=1 and y=-1
- Its shape is similar to the graph of
What other features of the hyperbolic functions and graphs do I need to know?
- The graphs of y=sinhx and y=tanhx have rotational symmetry about the origin
- This means that
- and are therefore odd functions
- This means that
- The graph of y=coshx is symmetrical in the y-axis
- This means that
- is therefore an even function
- This means that
What may I be asked to do with hyperbolic functions and their graphs?
- Sketch graphs and transformations
- e.g.
- Write as a transformation of and apply the transformations in the correct order
- Where possible label the key features of the transformed graph
- Intersections with the coordinate axes
- Equations of any asymptotes
- Coordinates of any turning points
- e.g.
- Find exact values
- e.g. Find the exact value of
- Use the definitions to write in terms of e
- Use and
- e.g. Find the exact value of
Examiner Tip
- When using a calculator make sure you use sinh, cosh and tanh and NOT sin, cos and tan
- Questions asking for values in exact form are often easier “to see” without a calculator, using the definitions of sinh and cosh, rather than trying to type in a complicated expression with e and ln
Worked example
a)
Find the exact values of
(i)
(ii)
b)
Sketch the graph of , labelling any points where the graph crosses the coordinate axes and any turning points.