# Trig Formulae and Trig equations Flashcards

1
Q

What is the Double Angle Formulae

A

sin2A = 2sinAcosA
cos2A = 2cos2A - 1
= 1 - 2sin2A
= cos2A – sin2A

2
Q
```3cos2x – 5cosx – 2 = 0
what happens when you
Let p = cosx
p = ?
x = ?
cosx = ?```
A
```3p2 – 5p - 2 = 0
(3p + 1)(p -2) = 0
p = cosx = 1/3
x = cos-1( 1/3)
x = 109.5 and 250.5
cosx = 2```
3
Q

The exact value of sinx

A
```sinx = 2sin(x/2)cos(x/2)
sinx = 2 (¼ + √(42 - 12) )
sinx = ½ + 2√15)```
4
Q

A

sin(A ± B) = sinAcosB cosAsinB
+
-
cos(A ± B) = cosAcosB sinAsinB

5
Q

What do we consider to be the double angle formulae

A

sin2A and cos2A

6
Q

Formulae for sin (A + B) and cos (A + B)

A

ssin(A ± B) = sinAcosB cosAsinB
+ = tan (A + B)
- tanA + tanB
cos(A ± B) = cosAcosB sinAsinB 1 - tanA tanB

7
Q

How are the addition formulae appear?/ what does it look like?

A

(a + β)

8
Q

why is the addition formulae used?

A

to express the sine and cosine of the sum of two angles in term of sines and cosines of the individual angles