Trigonometry

What numeracy skills do I need to learn in my D&T lessons?

a) Length   →   b) Weight   →   c) Perimeter   →   d) Capacity   →   e) Area   →   f) Volume   

What other mathematics skills can I learn using this site?

g) Multiplication   →   h) Angle   →  i) Trigonometry  →   j) Algebra   →  

What is Pythagoras's Theorem?

Named after the Greek philosopher Pythagoras (who didn't create it but popularised it), this helps us find a missing side length in a right-angled triangle as long as two other side lengths are known.  BEWARE - This ONLY works for RIGHT-ANGLED  TRIANGLES!

What are sine, cosine and tangents?

'Sine' and 'Cosine' values can be thought of as the coordinates of a point that sits on a circle in relation to the centre of the circle. 'Sine' represents the X coordinate and 'Cosine' represents the Y coordinate. They are both unitless properties (they don't carry units). 

A 'tangent' can be thought of as the slope of the projected line as it intersects the circle. Since it is always the sine divided by the cosine (i.e. a fraction or division) it too is unitless. If you drew a line from the circle at the end of the X axis until it 'hits' the projected line, that would be the tangent. 

All three properties are essential to understanding trigonometry and the 'SOH-CAH-TOA' relationship. 

Using the sine and cosine rules

Where triangles are concerned, if you know 2 values (angles or side lengths), then you can find a third. There are two 'rules' (i.e. expressions) for doing this; the 'Sine rule' and the 'Cosine rule'. Depending upon what you know (or have been 'given'), then this will determine which of the rules you will need to use.