# My Studies Diary

## 07/04/19

### Volume of Objects

Volume = area of base x height

Area of Base = length x width

To work out the volume of a cone, vs a cylinder, we work out the volume of the cylinder and then divide by 3. The volume of a cone is a third of a cylinder.

**volume of a cone**is pi times the radius squared times the height divided by 3

## 06/04/19

#### Angles & Triangles

supplementary angle – either of two angles whose sum is 180°.

When two lines are crossed by another line (called the Transversal), the angles in matching corners are called *Corresponding Angles*.

*Vertical Angles*are the

*angles*opposite each other when two lines cross. “

*Vertical*” in this case means they share the same Vertex (corner point), not the usual meaning of up-down.

All squares have four right angles and four sides that are equal in length.

*Equilateral* definition, having all the sides equal: an *equilateral* triangle.

For a triangle to be equilateral, it must also have equal angles. Every triangle’s three angles sum to 180. 180 divided by 3 is 60. 60 is less than 90. Angles are either right, which is to say 90 exactly, or obtuse, which is to say greater than 90 and less than 180, or acute, which is to say less than 90. An acute triangle is one in which all three angles are acute. Equilateral triangles are all acute.

**isosceles triangle** is a **triangle** that has two sides of equal length. an **equilateral triangle** is a **triangle** in which all three sides are equal. A **scalene triangle** is a **triangle** that has three unequal sides.

An **acute triangle** (or **acute**-angled **triangle**) is a**triangle** with three **acute** angles (less than 90°). An **obtuse triangle** is a **triangle** in which one of the angles is an **obtuse** angle.

#### Circle Pi Area Circumference & More

The circumference is the outside perimeter of a **circle**. It’s the distance around a **circle**. A **radius** can be a line from any point on the circumference to the center of the **circle**. If you put two **radii** together, edge to edge, going through the center of a **circle**, you would get a diameter.

We have a formula that **relates** these two parts of a circle. This formula is called the **circumference** formula, and it is C = pi*d where C stands for the **circumference** and d stands for the **diameter**. And pi is pi or 3.14.

**Formula** for **Area** of **circle**. The **formula** to **find** a **circle’s area** (radius)^{2} usually expressed as π ⋅ r 2 where r is the radius of a **circle**. The **area of a circle** is all the space inside a **circle’s** circumference.

Circumference: C=π⋅d or C=2π⋅r

## 31/03/19

While so does How do we know which form to use? **When writing normalized scientific notation, the coefficient must be greater than 1 and less than 10.**

Take 835,000

Move the decimal point to the first digit, so 8.35000 and then count how many places after the decimal point. There are 5 places after the decimal point so this number is 10^5.

So we get 8.35 x 10^5.

This is cold scientific notation and it is a method of representing very large or very small numbers.

Also written using E