Trigonometry — Formula Sheet

sin A = BC/AC = (opposite side)/(hypotenuse)

cos A = AB/AC = (adjacent side)/(hypotenuse)

tan A = BC/AB = (opposite side)/(adjacent side)

cosec A = 1/sin A = Hypotenuse/Opposite side

sec A = 1/cos A

sin 0° = 0

cos 0° = 1

sin 90° = 1

cos 90° = 0

cos^2 A + sin^2 A = 1

1 + tan^2 A = sec^2 A

cot^2 A + 1 = cosec^2 A

sin(90°-A)=cos A

cos(90°-A)=sin A

tan(90°-A)=cot A

cot(90°-A)=tan A

sec(90°-A)=cosec A

tan A = sin A / cos A.

For an acute angle A in a right-angled triangle, sin A = BC/AC, cos A = AB/AC, and tan A = BC/AB.

cosec A = 1/sin A, sec A = 1/cos A, and cot A = 1/tan A.

cos^2 A + sin^2 A = 1.