As we know, there are an infinite number of answers. We will find the first 2 positive angles whose cosine is `0.7`.
From our calculator, we have one answer: cos-10.7 = 45.57°.
Since this is an acute angle, we can use it as the reference angle and write α = 45.57°.
To find another answer, we remember that the 2 places where cosine is positive are the first (I) and fourth (IV) quadrants. The corresponding angle in the fourth quadrant will be:
360° − α = 360° − 45.57° = 314.43°
Check: cos 45.57° = 0.7000373 and
cos 314.43° = 0.7000373
Of course, there are an infinite number of angles where the cosine of the angle is `0.7`. Here are some of them (the values where the red arrows are pointing):
Try the values in your calculator (eg cos 1125.6°) to convince yourself that they are correct. (Your answer rounded to one decimal place should be `0.7` for each one.)
Checking your answers helps you to understand what is going on and it is great for building confidence in mathematics!