Area of a Triangle (Edexcel IGCSE Maths)

How do I find the area of a non-right triangle?

• The area of any triangle can be found using the formula

• • Where C is the angle between sides a and b

• • You need to remember it
• Be careful to label your triangle correctly so that C is always the angle between the two sides
• Sin 90° = 1 so if C = 90° this becomes Area = ½ × base × height
• If you know the area you can use the formula to find the length of a side or the angle
  • Using inverse sin will always give you an acute angle
  • Subtract the value from 180 if you need the obtuse angle