Answer:
Sin, Cos, Tan and others are used to calculate the ratios of the sides of a right angled triangle by taking a certain angle as the angle of reference.
On the other hand, Sin‐¹, Cos‐¹ and Tan-¹ are used to find the reference angle used to calculate the ratio of sides.
For this question,
we need to find which option should used to calculate the angle the slide makes with the vertical support.
So the option will have to be either A, C or E.
here, the base is 2.81m and hypotenuse is 3.64m.
we know, Cos = base / hypotenuse
So the angle is given by Cos-¹(2.81/3.64)
Option C
The porosity of the gravel sample is 28.75%
We have to determine.
What is the porosity of the gravel sample?
<h3>The porosity of the gravel sample;</h3>
Porosity is the term which is defined as the volume of voids present in the soil to the total volume of the soil.
The formula used to calculate the Porosity is;

A sponge is a case of a permeable fabric because it incorporates a huge number of purge spaces compared to its volume.
Porosity is the property of a question that communicates the entire volume of purge or pore space within the material.
Hence, the porosity of the gravel sample is 28.75%
Learn more about "porosity" :
brainly.com/question/2593663
729 wish you well on your assignment ~JyMarkus
-2(5,6)-40 I think that's it