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Reading the Midline

Part of the Graphs of Trig Functions section of Coddy's Trigonometry journey. Lesson 21 of 49.

To read y = a cos(x) + k from a graph, do the heights first. Take the highest and lowest values: halfway is k, half the gap is the size of a. Then look at x = 0 for the sign of a: a cosine with a positive a is at its top there, with a negative a at its bottom.

$A wave between 1 and 5, at its bottom at x = 0$

This wave runs from 1 to 5, so k = 3 and the size of a is 2. At 0 it is at its bottom, so a is negative: $y = -2\cos\left(x\right)+3$ .

Challenge

Write the equation of the wave in the graph tile in the form $y = a\cdot \cos\left(x\right)+k$ . Press Check.

Try it yourself

Write the equation of the graph

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

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