Fractions and Decimals
Ratio and Proportion
Indices & Standard Form
Algebra and Graphs
Trig Word Problems
Sine and Cosine Rule
Area of any Triangle
Angles of Elevation/Depression
Vectors, Matrices and Transformations
Collecting and displaying data
How to calculate the Area of any triangle
A long time ago (have a look over here if you have forgotten) we have learned that to find the area of a triangle, we multiply the base by the height and then divide that answer by two (or multiply by one half). An essential part of that formula is that the base and the height need to make a 90 degree (perpendicular) angle (for actually you are calculating the area of half a rectangle). Now we will learn how to calculate the area of any triangle even when you are not given a perpendicular angle:
Area = 0.5 x a x b x sinC
This formula, as you will find out in Part 2, is still based upon multiplying the height by the base by one half. I therefore encourage you to study Part 2 so you understand what you are doing and realise you are not performing some magic trick. The formula helps us however to increase our pace when finding the area of triangles in the absence of a right angle. There is a big chance you will be asked this type of question on your GCSE / IGCSE maths exam.
If you have studied the previous questions, it is time to try some example questions on this important GCSE IGCSE Maths topic. Make sure to study both parts (part 3 and 4) for they deal with different situations. When you open the video, pause it and try to answer the questions yourself first before having a look at my workings and answers. Please do not hesitate to contact me if you still have a question or problem. Good luck and have fun!!
Activity Trigonometry - Area of a triangle
When you have examined all of the videos you can try to worksheet below during your maths revision. You can answer the questions online or download the file on your computer and solve the questions offline (please consider the environment and decide whether you really need to print the worksheet or not). I have included the answer key which you will find on the second page of the document. So get started and pass your next maths exam! Good luck and have fun finding the area of triangles using trigonometry!