Calculate cos^-1(-3)

Step by step

The question

Question: find cos⁻¹(−3).

1 What it asks

cos⁻¹ of −3 means: the angle whose cosine is −3.

We call that angle θ.

So cos θ = −3.

Cos θ is the across value of a point on the unit circle.

The circle has radius 1.

So it is never more than 1 or less than −1.

−3 is less than −1.

So no angle works: cos⁻¹(−3) has no answer.