If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Solve sinusoidal equations (basic)

You might need: Calculator


Jamie tried to solve the following equation, where x is in radians to the nearest hundredth, in the interval from π to π, but she made a mistake.
Here is Jamie's work.
cos1(cos(x))=cos1(0.08)x1.65Using cos(x)=cos(x+2π)x1.65+2πnx4.631.657.93Using cos(x)=cos(πx)and cos(x)=cos(x+2π)x1.49+2πnx4.791.497.77
The solutions to x in the interval from π to π are x1.49 and x1.65.
What was Jamie's mistake?
Choose 1 answer: