Trigonometry

Trigonometry

Sine and cosine rule

Cosine rule:

 $a^2=b^2+c^2-2bc\ \cos A$  
Sine rule:
 $\frac{a}{Sin\ A}=\frac{b}{Sin\ B}=\frac{c}{Sin\ C}$  
Area of triangle
 $Area\ =\frac{1}{2}ab\ \sin\ C$  

Cosine rule

Missing side

Poll

What would you use here?

• Sine rule

• Pythagoras

• Trigonometry

• Cosine rule

Poll

Which is the correct rearrangement of the cosine rule?

 $\frac{ }{ }$  

•  $\cos\ A\ =\ \frac{b^2+c^2+a^2}{2bc\ \cos\ A}$  

•  $\cos\ A\ =\ \frac{b^2-c^2-a^2}{2bc\ \cos\ A}$  

•  $\cos\ A\ =\ \frac{b^2+c^2-a^2}{2bc\ \cos A}$  

Poll

What would you use here?

• Sine rule

• Pythagoras

• Trigonometry

• Cosine rule

Multiple Choice

Which is the correct equation?

Area of a triangle (no right angles)