Form 4 - Math formulas

Pythagorean Theorem: Find the hypotenuse

a² + b² = c²

c² = √ans

c = ans

Pythagorean Theorem: Find the side

c² - b² = a² or c² - a² = b²

c² - b² = a²

a² = √ans

a = ans

Sin

Opposite/Hypotenuse

Cos

Adjacent/Hypotenuse

Tan

Opposite/Adjacent

If the missing length on; Top

Multiple

If the missing length on; Bottom

Divide

Top

Trig ratios x number

Bottom

number ÷ Trig ratios

Finding missing angles

Side ÷ Side = Ans [3 significant figures]

Trig ratios-1 (Ans [3 significant figures])

Finding the bearing

• Identify the ‘Form pont’

• Draw a North line on the ‘Form pont’

• Go into a clockwise direction

Gradient (m)

Finding the (i) midpoint of a line segment

Finding the length of a line segment (distance between 2 points)

Simple Interest

Compound Interest

Appreciation

Depreciation

Surface Area: Sphere

4ㅈr²

Surface Area: Cube

6L²

Surface Area: Cuboid

2LW + 2HW + 2LH

Surface Area: Wedge

1. Area of the Δ cross section: ½ bh

2.  Area of the ▭ Top:

3.  Area of the ▭ back:

4.  Area of the ▭ base:

TSA of Wedge = Area of the Δ cross section: ½ bh x 2 + Area of the ▭ Top + Area of the ▭ back + Area of the ▭ base.

Surface Area: Cone

ㅈr² + ㅈrh

Surface Area: Cylinder

2ㅈr² + 2ㅈrh

Volume: Pyramid

⅓ (Area of the base) x H

Volume: Cube

S³

Volume: Cuboid

LWH

Volume: Cone

⅓ ㅈr²h

Volume: Sphere

4/3 ㅈr³

Volume: Cylinder

ㅈr³h

The angle at the centre of a circle is twice the angle at the circumference when subtended by the same arc.

The angle formed in a semicircle (from the diameter to the circumference) is always 90°.

Angles formed in the same segment of a circle are equal.

Opposite angles are Supplementary; they add up to 180.

The two tangents drawn from an external point to a circle are equal in length.

The angle between a tangent and the radius at the point of contact is 90°.

Alternate Segment Theorem

• ∠(tangent, chord) = ∠(angle in opposite arc)

Hire Purchase Price

Hire Purchase Price=Cash Price+Interest

Interest

Deposit

Amount to be Paid in Installments

Installment Amount=(Cash Price−Deposit)+Interest

Monthly Installment

To Find a Percentage of a Number

To Find the Whole from a Part

To Find the Percentage from a Part and Whole

Mortgage

𝑀

M = monthly payment

𝑃

P = loan amount (principal)

𝑟

r = monthly interest rate (annual rate ÷ 12)

𝑛

n = total number of monthly payments (years × 12)