which of the following is true?
a. tan^-1 (1) = - cot^-1 (1)
b. tan^-1 (-1)= cot^-1 (1)
c. tan^-1 (-1) = cot^-1 (-1)
d. tan^-1 (1) = cot^-1 (-1)

Question

which of the following is true? 
a. tan^-1 (1) = - cot^-1 (1)
b. tan^-1 (-1)= cot^-1 (1)
c. tan^-1 (-1) = cot^-1 (-1)
d. tan^-1 (1) = cot^-1 (-1)

anonymous · Answer

letter C i got it

anonymous · Answer

i use wolf alpha here every answer make it false unless letter c..i just need a pro who say im wrong or im correct.

anonymous · Answer

yeh sorry I was afk...give me a few mins

anonymous · Answer

no its ok =)

anonymous · Answer

ok, well tan (pi/4)=1 so tan^-1(1)=(pi/4) and similarly, tan(-pi/4)=-1 so tan^-1(-1)=-(pi/4).  Also, cot (pi/4)=1 so cot^-1(1)=(pi/4).  Similarly, cot(-pi/4)=-1 so cot^-1(-1)=-pi/4.  Checking our answers against the above considerations shows that you are correct, c is true.

anonymous · Answer

thanks help a lot