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

2 Answers
Aug 19, 2016

#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°#

Aug 22, 2016

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Using my now very outdated Casio fx-9700GE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