DEPRECATED Understanding inverse trig functions

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Problem

Shreya is an air traffic controller. One day, a plane was blown off course during a storm, and its navigational equipment was damaged. Over the radio, the plane's pilot reports that the cosine of an angle is 0, point, 64 and this angle is larger than start fraction, pi, divided by, 2, end fraction radians. She needs to figure out the measure of this angle to guide the plane to safety.
What should Shreya do to find the angle?
Please choose from one of the following options.