If
secθ−tanθ
secθ+tanθ
=
3
5
, 0
∘
<θ<90
∘
, then what is the value of (cscθ+cosθ+cotθ)?
- A2
4+
15
- B4
8+3
15
- C4
8+5
15
- D4
16+5
15
Solution & Step-by-step Explanation
Given:
secθ−tanθ
secθ+tanθ
=
3
5
Applying Componendo and Dividendo:
(secθ+tanθ)−(secθ−tanθ)
(secθ+tanθ)+(secθ−tanθ)
=
5−3
5+3
2tanθ
2secθ
=
2
8
sinθ/cosθ
1/cosθ
=4⟹
sinθ
1
=4⟹sinθ=
4
1
From sinθ=
4
1
:
cscθ=4
cosθ=
1−sin
2
θ
=
1−
16
1
=
4
15
cotθ=
sinθ
cosθ
=
1/4
15
/4
=
15
Substitute these values into the required expression:
cscθ+cosθ+cotθ=4+
4
15
+
15
=4+
4
15
+4
15
=4+
4
5
15
=
4
16+5
15
secθ−tanθ
secθ+tanθ
=
3
5
Applying Componendo and Dividendo:
(secθ+tanθ)−(secθ−tanθ)
(secθ+tanθ)+(secθ−tanθ)
=
5−3
5+3
2tanθ
2secθ
=
2
8
sinθ/cosθ
1/cosθ
=4⟹
sinθ
1
=4⟹sinθ=
4
1
From sinθ=
4
1
:
cscθ=4
cosθ=
1−sin
2
θ
=
1−
16
1
=
4
15
cotθ=
sinθ
cosθ
=
1/4
15
/4
=
15
Substitute these values into the required expression:
cscθ+cosθ+cotθ=4+
4
15
+
15
=4+
4
15
+4
15
=4+
4
5
15
=
4
16+5
15