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Sine waves – trigonometry – math

By |2017-07-29T17:59:39+00:00July 29th, 2017|Math|

Sine wave In order to save energy, many, many things in nature move in a kind of repeated pattern we call a sine wave: water waves, sound waves, light waves, electricity, radio waves, and microwaves, for instance. The waves move in one direction quickly, then slow down until they stop, and begin moving [...]

Cosine – Trigonometry – Math

By |2017-07-29T17:48:21+00:00July 29th, 2017|Math|

Right triangle and cosine A cosine, like a sine, is a mathematical way of thinking about a kind of movement that happens in nature. A cosine is really just a rephrasing of the same information we already had for calculating the sine function. One way to describe these changes is with the sine function. Choose [...]

What is a trapezoid? Simple geometry

By |2017-07-29T13:16:13+00:00July 29th, 2017|Math|

This is a trapezoid. A trapezoid is a kind of quadrilateral that has at least two sides that are parallel to each other. A parallelogram is a trapezoid that has two pairs of parallel sides, and a rhombus is a special kind of parallelogram, and so are rectangles and squares. To figure out the perimeter of a trapezoid, you can add the lengths of [...]

What is a square? Simple geometry

By |2018-04-23T16:01:49+00:00July 29th, 2017|Math|

This is a square. The darker purple line is the perimeter of the square. A square is a flat shape, in one plane, defined by four points at the four corners. A square has four sides all of equal length, and four corners, all right angles (90 degree angles). So a square is a kind of rectangle. To figure [...]

Rectangle – area and perimeter

By |2018-04-23T16:01:22+00:00July 29th, 2017|Math|

This is a rectangle. A rectangle is a flat shape, in one plane. It's defined by four points at the four corners. A rectangle has two sides of equal length opposite each other, and two other sides of equal length opposite each other, and four corners, all right angles (90 degree angles). A square is a special kind of rectangle. [...]

What is a quadrilateral? Squares and rectangles

By |2017-07-29T12:01:49+00:00July 29th, 2017|Math|

This is a quadrilateral. A quadrilateral is a flat shape, in one plane, defined by four points at the four corners. A quadrilateral has four sides. The sides can be of any length. And it has four corners. They can be at any angle  to each other so long as they add up to 360 degrees. A rectangle is [...]

Perpendicular lines – Simple geometry

By |2017-07-29T11:41:47+00:00July 29th, 2017|Math|

Perpendicular lines Two lines are perpendicular if they cross at right angles. You can test this by extending the lines until they cross (if they do not cross then they are parallel). Where the two lines cross, draw a right triangle, and then see whether the triangle conforms to the Pythagorean Theorem - if so, then your lines are crossing [...]