Proving the Pythagorean Identity
Precalculus · Flashcards · Application
PRECALCULUS · FLASHCARDS
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QUESTION
What is
tan
(
θ
)
\tan(\theta)
tan
(
θ
)
if
cos
(
θ
)
=
−
8
17
\cos(\theta)=-\frac{8}{17}
cos
(
θ
)
=
−
17
8
and
θ
\theta
θ
is in Quadrant II?
QUESTION
What is
sin
(
θ
)
\sin(\theta)
sin
(
θ
)
if
cos
(
θ
)
=
5
13
\cos(\theta)=\frac{5}{13}
cos
(
θ
)
=
13
5
and
θ
\theta
θ
is in Quadrant I?
QUESTION
Find
cos
(
θ
)
\cos(\theta)
cos
(
θ
)
if
sin
(
θ
)
=
3
5
\sin(\theta)=\frac{3}{5}
sin
(
θ
)
=
5
3
and
θ
\theta
θ
is in Quadrant I.
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ANSWER
cos
(
θ
)
=
4
5
\cos(\theta)=\frac{4}{5}
cos
(
θ
)
=
5
4
. Use
cos
2
=
1
−
sin
2
=
1
−
9
25
=
16
25
\cos^2=1-\sin^2=1-\frac{9}{25}=\frac{16}{25}
cos
2
=
1
−
sin
2
=
1
−
25
9
=
25
16
; QI means positive.
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