cos <mrow class="MJX-TeXAtom-ORD"> &#x2212;<!-- - --> 1 </mrow> </msup

Tananiajtac2

Tananiajtac2

Answered question

2022-06-03

cos 1 ( cos ( 8 π / 7 ) ) evaluation
I believe this to equal 6 π / 7 using a reference angle of π / 7, is this thinking correct or do the inverse of cos and cos just cancel out? It's been awhile since I've done trig and I can't recall the proper rules for this.

Answer & Explanation

Carlos Nicholson

Carlos Nicholson

Beginner2022-06-04Added 4 answers

You have
cos a = cos b a = 2 k π ± b
and by the usual definition, the arc cosine returns the only angle in range [ 0 , π ].
In your case,
2 π 8 π 7 = 6 π 7 .

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?