# pythagoras and trigonometry notes

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pythagoras' theorem

a squared + b squared = c squared   (C grade)

• only works for right angled triangles
• uses 2 sides to find the 3rd side
• make sure you get the numbers in the right place
• c is the longest side (called the hypotenuse) and it's always opposite the right angle

use pythagoras to find the distance between two points (c grade)

• draw a sketch to show the right-angled triangle
• find the lengths of the shorter sides of the triangle
• use pythagoras to find the length of the hypotenuse

trigonometry- Sin, Cos, Tan

the 3 trigonometry formulas (b grade)

• three basic trig formulas
• each one links two sides and an angle of a right-angled triangle
• sin x = opposite divided by hypotenuse
• cos x = adjacent divided by hypotenuse
• tan x = oppositve divided by adjacent
• hypotenuse is the longest side
• opposite is the side opposite the angle being used
• adjacent is the side next to the angle being used
• work out which two sides of the triangle are involved in the question
• pick the formula that involves those sides
• to find the angle- use the inverse followed by sin, cos or tan
• make sure your calculator is in deg mode
• your calculator will display sin, cos or tan to the power of -1
• only works for right angled triangles

angles of elevation and depression (b grade)

• angle of depression is angle downwards from the horizontal
• angle of elevation is angle upwards from the horizontal