Maths: Formulas

Question 1

How do you calculate percentage change?

Answer 1

(change in amount / original amount) x 100

Question 2

What is Pythagoras’ theorem?

Answer 2

A² + B² = C²

Question 3

What does SohCahToa stand for?

Answer 3

Sine = O/H Cosine = A/H Tangent = O/A

Question 4

What are the 3 sides of a right angled triangle called?

Answer 4

Opposite, Adjacent, Hypotenuse

Question 5

What formula would you use with Opposite & Adjacent

Answer 5

Cosθ = A/H

Question 6

What formula would you use with Opposite & Hypotenuse

Answer 6

Sinθ = O/H

Question 7

What formula would you use with Adjacent & Opposite

Answer 7

Tanθ = O/A

Question 8

What formula is used to find missing sides in trigonometry?

Answer 8

Sin/Cos/Tan (θ) = O/H or O/A or A/H

Question 9

What is the formula for area of trapezium?

Answer 9

(A+B)/2 x height

Question 10

What is the formula for the total sum of interior angles of a polygon?

Answer 10

(n-2) x 180°
n is the number of sides
e.g pentagon
(5-2) x 180° = 540°

Question 11

What is a Polygon?

Answer 11

A 2D shape with straight sides (not a circle) e.g rectangles, pentagons, octagons

Question 12

Compare a regular polygon vs an irregular polygon

Answer 12

Regular Polygon:
Equal angles
Equal side lengths

Irregular Polygon:
Different Angles
Different side lengths

Question 13

What is the formula for one interior angle of a polygon?

Answer 13

(n-2) x 180° / n
n is the number of sides
e.g pentagon
(5-2) x 180° = 540°
540°/5 = 108°

Question 14

What is the total sum of all exterior angles of a polygon?

Answer 14

360°

Question 15

How do you work out the sum of one exterior angle of a polygon?

Answer 15

360°/n
n is the number of sides
e.g pentagon
360°/5 = 72°

Question 16

What are the types of pairs of angles in parallel lines?

Answer 16

Vertically opposite - Equal
Co-interior - add up to 180°
Corresponding - Equal
Alternate - Equal
Angles on a straight line - add up to 180°

Question 17

How do you find missing angles in trigonometry?

Answer 17

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°

Question 18

What is the formula for Pythagoras in 3D?

Answer 18

1. Use A² + B² = C² to find the hypotenuse
2. Use A² + B² = C² to find the 3D length that goes through the shape