9

Question 1

What trig identities are odd?

Answer 1

Sin, csc
tan, cot

Question 2

Which trig identities are even?

Answer 2

Cos, sec

Question 3

cofunction of sin

Answer 3

sin (π/2 - θ) = cos θ

Question 4

cofunction of cos

Answer 4

cos (π/2 - θ) = sin θ

Question 5

cofunction of tan

Answer 5

tan (π/2 - θ) = cot θ

Question 6

cofunction of cot

Answer 6

cot (π/2 - θ) = tan θ

Question 7

cofunction of sec

Answer 7

sec (π/2 - θ) = cosec θ

Question 8

cofunction of csc

Answer 8

csc (π/2 - θ) = sec θ

Question 9

3 Pythagorean Identities

Answer 9

sin^2θ+cos^2θ=1
1+cot^2θ=csc^2θ
tan^2θ+1=sec^2θ

Question 10

Sum identity of Cos

Answer 10

cos(α+β)=cos(α)cos(β)−sin(α)sin(β)

Question 11

Sum Identity of Sin

Answer 11

sin(α+β)=sin(α)cos(β)+cos(α)sin(β)

Question 12

Sum Identity of Tan

Answer 12

Tan(α+β)=tan(α)+tan(β) ÷ 1−tan(α)tan(β)

Question 13

Difference Identity of Cos

Answer 13

cos(α−β)=cosαcosβ+sinαsinβ

Question 14

Difference Identity of Sin

Answer 14

sin(α−β)=sinαcosβ−cosαsinβ

Question 15

Difference Identity of Tan

Answer 15

tan(α-β)=tan(α)-tan(β)÷1+tan(α)tan(β)

Question 16

Double Angle Identity of sin

Answer 16

sin 2θ = 2 sin θ cos θ

Question 17

Double Angle Identity of tan

Answer 17

tan 2θ =
2 tan θ ÷
1 − tan2 θ

Question 18

Double Angle Identity of cos

Answer 18

cos 2θ = cos^2 θ − sin^2 θ
cos2θ = 2cos^2θ - 1
cos2θ = 1 - 2sinθ^2