Answer:
a) 54π cm³
Step-by-step explanation:
area of circle=πr²
9π
π9*6=54π
Answer: r = 4 sec θ
Explanation: Using: x = r cos θ then r cos θ = 4 ⇒ r = 4 cos θ = 4 sec θ
Convert the mixed fractions into improper fractions and divide them to get them into decimals. Then see if pi is in between those numbers.
Ex: 2 3/4 = 11/4 = 2.75
Yes
The rule to check if a triplet of numbers can represent the sides of a triangle is the following: the sum of the length of two sides must exceed the third one.
This happens for all possible couples in your case:



5x - 100 + x - 20 = 180 (sum of supplementary angles is equal 180)
6x - 120 = 180
6x = 300
x = 50
x - 20 = 50 - 20 = 30
so
3y = 30 (vertical angles are equal)
y = 10