Asked by Lucy
Draw a picture and show all work.
Given cosA=3/10 and tanA<0, find sinA
Given cosA=3/10 and tanA<0, find sinA
Answers
Answered by
Reiny
This looks like a major homework or assignment dump without any effort or work shown on your part.
I will do this one, and help you with the others once you tell me more about what problems you have with these.
cosA = 3/5 and tanA is negative.
From your CAST rule, you know that the cosine is positive and the tangent is negative only in quadrant IV
So, as suggested did you sketch your triangle?
you know cos A = adjacent/hypotenus = x/r = 3/5
so you have x = 3, r = 5 and y = ?
Did you recognize the 3,4,5 right-angled triangle?? IF not, then
x^2 + y^2 = r^2
9 + y^2 = 25
y^2 = 16
y = ± √4, but we are in quad IV, so y = -4
sinA = y/r = -4/5
I will do this one, and help you with the others once you tell me more about what problems you have with these.
cosA = 3/5 and tanA is negative.
From your CAST rule, you know that the cosine is positive and the tangent is negative only in quadrant IV
So, as suggested did you sketch your triangle?
you know cos A = adjacent/hypotenus = x/r = 3/5
so you have x = 3, r = 5 and y = ?
Did you recognize the 3,4,5 right-angled triangle?? IF not, then
x^2 + y^2 = r^2
9 + y^2 = 25
y^2 = 16
y = ± √4, but we are in quad IV, so y = -4
sinA = y/r = -4/5
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