SOLUTION: If cosθ=-3/5, find cos(π/2-θ). Write your answer as a fraction.

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Question 1186273: If cosθ=-3/5, find cos(π/2-θ). Write your answer as a fraction.
Found 2 solutions by MathLover1, ikleyn:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

If cos%28theta%29=-3%2F5=> adj=-3 and hyp=5
then
opp=sqrt%285%5E2-%28-3%29%5E2%29
opp=sqrt%2816%29
opp=4 or opp=-4
so, sin%28theta%29=4%2F5 or sin%28theta%29=-4%2F5
since cos%28pi%2F2-theta%29=sin%28theta%29, we have
cos%28pi%2F2-theta%29=4%2F5 or cos%28pi%2F2-theta%29=-4%2F5

Answer by ikleyn(52848) About Me  (Show Source):
You can put this solution on YOUR website!
.

Listen to me attentively:  it is  VERY  IMPORTANT.



@MatLover1 gave one single answer,  but the problem,  as it is given in the post,
has  TWO  possible answers.


            They are  PLUS  or  MINUS  values given by @MathLover1.


It is because  EVERY  SQUARE  ROOT  has two values:  one positive and one negative.


Based on given condition,  it is not possible to say which one of the two values is the answer:
they  BOTH  are answers.


To extract a unique answer,  the problem  MUST  SPECIFY  to which quadrant the given angle  theta  does belong.

Since the problem does not provide this info,  the posted condition is  DEFECTIVE.


Or the answer by  @MathLover1 is incomplete.


You can treat it  IN  EITHER  WAY.