Find an angle from a trigonometric ratio

Acute angle

\(\displaystyle \cos\theta=0.58\)

Which calculator operation finds the angle in degrees?

Move the trial angle. Find two neighbouring whole-degree positions whose cosine values lie on opposite sides of the target

Between which trial angles does the target occur?

Reverse the calculator calculation

Trial angles helped locate the answer. The matching inverse key finds it directly. Here every requested angle is acute

1. 1Choose the matching inverse The stated ratio names the key. Inverse sine, inverse cosine and inverse tangent each recover an angle from their own ratio \(\displaystyle \begin{aligned}\sin\theta=v&\;\Longrightarrow\;\theta=\sin^{-1}(v)\\\cos\theta=v&\;\Longrightarrow\;\theta=\cos^{-1}(v)\\\tan\theta=v&\;\Longrightarrow\;\theta=\tan^{-1}(v)\end{aligned}\)
2. 2Use degree mode The inverse key returns an angle. Degree mode gives the requested angle unit
3. 3Round the final angle Enter the complete supplied ratio. Keep the calculator output until you round the answer to the requested precision

Acute angle

\(\displaystyle \sin\theta=0.837\)

Find the angle in degree mode, to one decimal place

Use the inverse key for the named ratio

Acute angle

\(\displaystyle \cos\theta=0.58\)

Calculate the angle to one decimal place in degree mode

Use inverse cosine rather than the cosine key

Acute angle

\(\displaystyle \tan\theta=1.73\)

Find the angle to one decimal place. Use degree mode

A tangent value greater than one is valid. Apply inverse tangent

Acute angle

\(\displaystyle \tan\theta=1.73\)

Which change fixes the first line?