Maths: Formulas Flashcards
How do you calculate percentage change?
(change in amount / original amount) x 100
What is Pythagoras’ theorem?
A² + B² = C²
What does SohCahToa stand for?
Sine = O/H Cosine = A/H Tangent = O/A
What are the 3 sides of a right angled triangle called?
Opposite, Adjacent, Hypotenuse
What formula would you use with Opposite & Adjacent
Cosθ = A/H
What formula would you use with Opposite & Hypotenuse
Sinθ = O/H
What formula would you use with Adjacent & Opposite
Tanθ = O/A
What formula is used to find missing sides in trigonometry?
Sin/Cos/Tan (θ) = O/H or O/A or A/H
What is the formula for area of trapezium?
(A+B)/2 x height
What is the formula for the total sum of interior angles of a polygon?
(n-2) x 180°
n is the number of sides
e.g pentagon
(5-2) x 180° = 540°
What is a Polygon?
A 2D shape with straight sides (not a circle) e.g rectangles, pentagons, octagons
Compare a regular polygon vs an irregular polygon
Regular Polygon:
Equal angles
Equal side lengths
Irregular Polygon:
Different Angles
Different side lengths
What is the formula for one interior angle of a polygon?
(n-2) x 180° / n
n is the number of sides
e.g pentagon
(5-2) x 180° = 540°
540°/5 = 108°
What is the total sum of all exterior angles of a polygon?
360°
How do you work out the sum of one exterior angle of a polygon?
360°/n
n is the number of sides
e.g pentagon
360°/5 = 72°
What are the types of pairs of angles in parallel lines?
Vertically opposite - Equal
Co-interior - add up to 180°
Corresponding - Equal
Alternate - Equal
Angles on a straight line - add up to 180°
How do you find missing angles in trigonometry?
use the inverse of the trigonometric ratios
e.g. sin⁻¹ or cos⁻¹ or tan⁻¹
e.g. sin⁻¹(O/H) = θ (in other words, the missing angle)
remember to substitute trigonometric values (opposite, adjacent and hypotenuse)
example: sin⁻¹(5/10) = 30°
What is the formula for Pythagoras in 3D?
- Use A² + B² = C² to find the hypotenuse
- Use A² + B² = C² to find the 3D length that goes through the shape
