Question

Evaulate Cos^-1 (tan pi/4).

Answer 1

start by finding tan pi/4

Answer 2

1

Answer 3

did this on the calculator and it gave 89.21

Answer 4

pi/4 is the same as 45 deg.
In a 45-45-90 degree triangle, the legs are congruent.
That means sin 45 = cos 45.
Since tan 45 = sin 45 / cos 45, then tan 45 = 1.
That takes care of tan (pi/4)
Now you need to do cos^_1 1
At what angle is the cosine equal to 1?

Answer 5

hint:
we have:
\(\tan(\pi/4)=1\)

Answer 6

cos^-1 (1)= 0 ?

Answer 7

better is: \(2k\pi\), where \(k=0,\;\pm1,\;\pm2,...\)