Formulas

Question 1

Sine rule

Answer 1

a/sin A = b/sin B = c/sin C
or
sin A/a = sin B/b = sin C/c
(if finding angle put the sin as denominator and vice versa for side)
(only gives acute angles)

use sine rule when u get 2 angles and 1 side (finding another side)

use sine rule when u get 1 angle and 2 sides(finding another angle)

when the angle is obtuse take 180-the angle u got

Question 2

Cosine rule

Answer 2

a2 = b2 + c2 - 2bc x cos A
(find side a, use when have 2 sides and 1 angle)

cos A = b2+c2-a2 / 2bc
(find angle A, use when have 3 sides and no angles)

Question 3

acute and obtuse angles relationship

Answer 3

sin ANGLE = sin (180 - ANGLE)
cos ACUTE = -cos (180-ACUTE)
for cos acute side is positive while the obtuse side is negative

Question 4

area of triangle ABC

Answer 4

area = 1/2 x SIDE 1 x SIDE 2 x sin( the angle in between the 2 sides)

area= 1/2 x ab x sin C

Question 5

A3-b3

Answer 5

=(a-b)(a2+b2)
=(a-b)(a2+2ab+b2)

Question 6

What’s the point of radian mode since deg and rad mode r the same

Answer 6

Rad mode is only used for trigonometry, toa cah soh

Question 7

π rad

Answer 7

180deg

Question 8

Sector area

Answer 8

X/360 x πr^2 (area of circle)

Where X is the angle of the sector subtended at the centre of the circle of radius r

Question 9

Arc length

Answer 9

X/360x 2πr (circumference of circle)

Where x is the angle subtended by the arc at the centre of the circle of radius r

Question 10

How to find x

Where x is the angle subtended at the centre of a circle with radius r by an arc of length s

Answer 10

x = s/r

(Angle subtended = arc length divided by radius)

Question 11

Sector area using radian =

Answer 11

(1/2)(r^2)(x)

(Half of radius square x angle subtended)

Question 12

1 rad =

Answer 12

180/π deg

Question 13

1deg =

Answer 13

π/180 rad