Quick Question

What is the trig identity for sin(x − π/2) illustrated in the following graph?

Answer

The graph of sin(x − π/2) can be obtained by shifting the graph of sin(x) (in red) to the right π/2 units. The resulting graph is of the function −cos(x) (in blue). Hence, the identity suggested by these graphs is sin(x − π/2) = −cos(x).


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