SOLUTION: find the exact value using a double angle identity sin(3pi/2)

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Question 1204119: find the exact value using a double angle identity
sin(3pi/2)
Found 2 solutions by ikleyn, greenestamps:
Answer by ikleyn(52832) About Me  (Show Source):
You can put this solution on YOUR website!
.

sin%283pi%2F2%29 = -1.    ANSWER


    It is a Table angle (= the angle from the Table).


       +----------------------------------------------------------------+
       |    So the value of sine of this angle can be considered as     |
       |  a PRIMARY information, similar to an axiom of parallel lines. |
       +----------------------------------------------------------------+


       (Same as the case  2 x 2 = 4  from the multiplication Table).


    Double angle identity is IRRELEVANT.

Solved.

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The conclusion

        A request in this post is semi-idiotic.


P.S.   Above,  I used the term  "semi-idiotic"  to make my statement as  " soft "  as possible.

Without this softening,  the statement is  " A request in the post is idiotic ".    100%  true.



Answer by greenestamps(13203) About Me  (Show Source):
You can put this solution on YOUR website!


I would think that the double angle formula is relevant when the problem says to use it to get the answer......

sin%283pi%2F2%29 = sin%282%283pi%2F4%29%29

Use sin%282x%29=2sin%28x%29cos%28x%29

sin%282%283pi%2F4%29%29

= 2sin%283pi%2F4%29cos%283pi%2F4%29

= %282%29%28sqrt%282%29%2F2%29%28-sqrt%282%29%2F2%29=-1

ANSWER: sin(3pi/2) = -1