Oh joy. Oh yes. It’s another awful maths post, so feel free just to skip right over this. I only type these things up because it’s actually really good revision. It actively encourages me to think about the maths, and I’m likely to see it again when I log in. So without further adue:

**Basic Functions:**

**y=sinx**

**y=cosx**

**y=tanx**

**cosecx=1/sinx**

**secx=1/cosx**

**cotx=1/tanx**

**P1 Identities**

1) **sinA/cosA = tanA**

2) **cos^2A + sin^2A = 1**

**P2 Extensions**

Divide 2) by cos^2A

3) **1 + tan^2A = sec^2A**

Divide 3) by sin^2A

4) **cot^2A + 1 = cosec^2A**

**Further Identities**

5) **sin(A + – B) = sinAcosB + – sinBcosA**

When A = B:

6) **sin2A = 2sinAcosA**

7) **cos(A + – B) = cosAcosB – + sinAsinB** (note the change of signs)

When A = B:

8) **cos2A = cos^2A – sin^2A**

Replace -sin^2A with cos^2 – 1:

9) **cos2A = 2cos^2A – 1**

Replace cos^2A with 1 – sin^2A

10) **cos2A = 1 – 2sin^2A**

11) **tan(A + – B) = (tanA + – tanB)/(1 – + tanAtanB)** (note the sign orders)

12) **sin^2.1/2A = 1/2(1 – cosA)**

13) **cos^2.1/2A = 1/2(1 + cosA)**

Okay, and believe it or not, that’s not everything ;_; – but I have to go to work now, so I’ll finish up later…

Hey thanx for that. Helped me too.

Hey thanx for that. Helped me too.