In developing an interval estimate, if the population standard deviation is unknown, a. the sample standard deviation must be used.
b. the standard deviation is arrived at using the range.
c. it is impossible to develop the interval estimate.
d. it is assumed that the population standard deviation is 1.

proofs involving isosceles triangles often require special consideration because an isosceles triangle has several distinct properties that do not apply to normal triangles.(more about triangle types) therefore, when you are trying to prove that two triangles are congruent, and one or both triangles, are isosceles you have a few theorems that you can use to make your life easier.

step-by-step explanation:

an isosceles triangle has two congruent sides and two congruent angles. the congruent angles are called the base angles and the other angle is known as the vertex angle. ∠bac and ∠bca are the base angles of the triangle picture on the left. the vertex angle is ∠abc

step-by-step explanation:

graph using a few selected

x         y

-1       15

0         6

1         2.4

2       0.96