Cos theta=pi/2 hint pi/2 is not an angle.

  • Thread starter jrjack
  • Start date
  • #1
111
0
cos theta=pi/2....hint pi/2 is not an angle.

Homework Statement


[tex]\cos\theta=\frac{\pi}{2}[/tex] HINT:The real number [itex]\frac{\pi}{2}[/itex] is not an angle.


Homework Equations





The Attempt at a Solution



I tried [itex]0=\cos^{-1} \frac{\pi}{2}[/itex], but that equals no solution.
And if [itex]\frac{\pi}{2}[/itex] were an angle the answer would be 0.

Am I solving this correctly?
 

Answers and Replies

  • #2
SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
11,398
1,045


What is an approximate value for π/2 numerically?
 
  • #3
111
0


[itex]\pi \approx 3.14[/itex] so [itex]\frac{\pi}{2}\approx 1.57[/itex]

and since [itex]\cos\theta=1.57, then...\theta=no solution, because: \cos\theta= -1\leq\theta\geq1[/itex]
 
  • #4
uart
Science Advisor
2,797
21


Hi jrjack. Are you at all familiar with complex numbers?
 
  • #5
111
0


I'm not sure, but NO SOLUTION is always one of the possible options.

Please explain further how to use complex numbers in this problem.
 
  • #6
rock.freak667
Homework Helper
6,223
31


I'm not sure, but NO SOLUTION is always one of the possible options.

Please explain further how to use complex numbers in this problem.

You might want to say no real solutions instead though.
 
  • #7
111
0


Of course, No Real Solution. Since we are not dealing with imaginary numbers in this lesson, I think that is appropriate. Thanks.
 
  • #8
uart
Science Advisor
2,797
21


Of course, No Real Solution. Since we are not dealing with imaginary numbers in this lesson, I think that is appropriate. Thanks.

Yes that was my point exactly. :)


If you are only dealing with real numbers there is no solution. If you are allowed to use complex numbers (real and imaginary) then there are solutions.
 

Related Threads on Cos theta=pi/2 hint pi/2 is not an angle.

  • Last Post
Replies
3
Views
25K
Replies
20
Views
5K
  • Last Post
Replies
1
Views
8K
  • Last Post
Replies
2
Views
6K
  • Last Post
Replies
10
Views
22K
Replies
5
Views
2K
Replies
1
Views
3K
Replies
7
Views
531
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
6
Views
6K
Top