Question

How do you evaluate using a calculator of `tan^-1(-1.7321)`?

Answer 1

`tan120° = -1.7321 and tan300° = -1.7321`

Explanation:

This question is asking "What angle(s) has a tan value of `-1.7321`

Step 1 . "In which quadrants is tan negative?"

From the CAST rule: `"pos in " 1st and 3rd rArr "neg in " 2nd and 4th`

Step 2 . Find the root angle. Find `tan^-1(+1.7321)`
This gives the acute angle in the 1st quadrant from which we can get the angles in the other quadrants.

`theta = tan^-1(+1.7321) = 60°`

Step 3 Find the angles in the 2nd and 4th quadrants:

2nd quadrant: `180°- theta = 180°-60° = 120°`

4th quadrant: `360°- theta =360° -60° =300°`

CHECK: use a calculator to verify that:

`tan120° = -1.7321 and tan300° = -1.7321`

These are the angles for `0<= theta<= 360°`

Answer 2

Method shown below.

Explanation:

You will have to do a hunt on your key pad.

Using my now very outdated Casio fx-9700GE

Shift then tan`-> tan^(-)`

Do not use the 'minus' key but use the 'negative' key. On my machine designated as `(-)` showing the brackets.

After using `(-)` type in 1.7321

After that I have to use the key marked 'EXE' . Yours may be labelled Ans

Whatever it is it is the one you would have to press make it solve something like 2+3