Khan Academy Trigonometry

5 week Recap of Khan AcademyTrigonometry

Introduction

I decided to use Khan Academy Trigonometry app because this app has everything relating  to Trigonometry.  It has 32 videos for Trigonometry understandings

 Week 1

This week we refreshed our memories on Sine Cosine Tangent Cotangent Secant Cosecant

Sin, Cos and Tan

A right-angled triangle is a triangle in which one of the angles is a right-angle. The hypotenuse of a right angled triangle is the longest side, which is the one opposite the right angle. The adjacent side is the side which is between the angle in question and the right angle. The opposite side is opposite the angle in question.
In any right angled triangle, for any angle:

The sine of the angle = the length of the opposite side
                                   the length of the hypotenuse

The cosine of the angle = the length of the adjacent side
                                      the length of the hypotenuse

The tangent of the angle = the length of the opposite side
                                      the length of the adjacent side

So in shorthand notation:
sin = o/h   cos = a/h   tan = o/a
Often remembered by: soh cah toa

Example

Find the length of side x in the diagram below:

The angle is 60 degrees. We are given the hypotenuse and need to find the adjacent side. This formula which connects these three is:
cos(angle) = adjacent / hypotenuse
therefore, cos60 = x / 13
therefore, x = 13 × cos60 = 6.5
therefore the length of side x is 6.5cm.

 The videos refreshes my memory and continues to keep the concept in my mind .