In a right triangle:
tan A = opp/adj
opp/adj = -2/3
opp = 2
adj = 3 (ignore the sign for now)
The angle lies in quadrant II where sin > 0, cos < 0, tan < 0
hyp = sqrt( 2^2+ 3^2) = sqrt(4+9) = sqrt(13)
sin A = opp/hyp = 2/sqrt(13) ( sine is positive)
cos A = adj/hyp = -3/sqrt(13) (cos is negative)
tan A = opp/adj = -2/3 (tan is negative)
cot A = 1/tan A = -3/2
sec A = 1/cos A = -sqrt(13) /3
csc A = 1/sin A = sqrt(13)/2
tan A = - 2/3 and A in second quadrant
r² = 2² + 3² = 13
r = √13
sin A = 2 / √13
cos A = - 3 / √13
Assuming a right triangle we have:
opp² + adj² = hyp²
i.e. 2² + 3² = 13 => hyp²
so, hyp = √13
Now, sinA = opp/hyp => 3/√13...positive as sinA > 0 in quadrant 2
And, cosA = adj/hyp => -3/√13..negative as cosA < 0 in quadrant 2
Also, secA => 1/cosA = -√13/3
and cosecA => 1/sinA = √13/3
and cotA => 1/tanA = -3/2
:)>
Hint:
sinA>0
cosA<0
tanA=sinA/cosA
and
sec^2(A)=1+tan^2(A)
do your own homework
sec(a)^2 - tan(a)^2 = 1
sec(a)^2 - (-2/3)^2 = 1
sec(a)^2 - 4/9 = 1
sec(a)^2 = 13/9
sec(a) = +/- sqrt(13) / 3
a is in Q2, so sec(a) < 0
sec(a) = -sqrt(13) / 3
cos(a) = -3 / sqrt(13) = -3 * sqrt(13) / 13
cot(a) = -3/2
csc(a)^2 - cot(a)^2 = 1
csc(a)^2 - (-3/2)^2 = 1
csc(a)^2 - 9/4 = 1
csc(a)^2 = 13/4
csc(a) = +/- sqrt(13) / 2
csc(a) > 0
csc(a) = sqrt(13) / 2
sin(a) = 2/sqrt(13) = 2 * sqrt(13) / 13
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Answers & Comments
In a right triangle:
tan A = opp/adj
opp/adj = -2/3
opp = 2
adj = 3 (ignore the sign for now)
The angle lies in quadrant II where sin > 0, cos < 0, tan < 0
hyp = sqrt( 2^2+ 3^2) = sqrt(4+9) = sqrt(13)
sin A = opp/hyp = 2/sqrt(13) ( sine is positive)
cos A = adj/hyp = -3/sqrt(13) (cos is negative)
tan A = opp/adj = -2/3 (tan is negative)
cot A = 1/tan A = -3/2
sec A = 1/cos A = -sqrt(13) /3
csc A = 1/sin A = sqrt(13)/2
tan A = - 2/3 and A in second quadrant
r² = 2² + 3² = 13
r = √13
sin A = 2 / √13
cos A = - 3 / √13
Assuming a right triangle we have:
opp² + adj² = hyp²
i.e. 2² + 3² = 13 => hyp²
so, hyp = √13
Now, sinA = opp/hyp => 3/√13...positive as sinA > 0 in quadrant 2
And, cosA = adj/hyp => -3/√13..negative as cosA < 0 in quadrant 2
Also, secA => 1/cosA = -√13/3
and cosecA => 1/sinA = √13/3
and cotA => 1/tanA = -3/2
:)>
Hint:
sinA>0
cosA<0
tanA=sinA/cosA
and
sec^2(A)=1+tan^2(A)
do your own homework
sec(a)^2 - tan(a)^2 = 1
sec(a)^2 - (-2/3)^2 = 1
sec(a)^2 - 4/9 = 1
sec(a)^2 = 13/9
sec(a) = +/- sqrt(13) / 3
a is in Q2, so sec(a) < 0
sec(a) = -sqrt(13) / 3
cos(a) = -3 / sqrt(13) = -3 * sqrt(13) / 13
cot(a) = -3/2
csc(a)^2 - cot(a)^2 = 1
csc(a)^2 - (-3/2)^2 = 1
csc(a)^2 - 9/4 = 1
csc(a)^2 = 13/4
csc(a) = +/- sqrt(13) / 2
csc(a) > 0
csc(a) = sqrt(13) / 2
sin(a) = 2/sqrt(13) = 2 * sqrt(13) / 13