Answer:
CSA of cylinder= 2πr(h+r)
=2 π×9 (21)
= 378π cm²
now
CSA of hole= 2πr
12π cm²
378x^3 , i think thats right.
Answer:
(
5
,
π
)
Step-by-step explanation:
−
5
=
r
cos
θ
88
[
1
]
0
=
r
sin
θ
8888
[
2
]
Squaring [1] and [2]:
25
=
r
2
cos
2
θ
0
=
r
2
sin
2
θ
Adding [1] and [2]:
25
=
r
2
cos
2
θ
+
r
2
sin
2
θ
Factor:
25
=
r
2
(
cos
2
θ
+
sin
2
θ
)
25
=
r
2
⇒
r
=
±
5
( use
r
=
5
)
