Find the height h of the building round your answer to the nearest unit. Therefore we use the Cosine Rule. The triangle is not right-angled. When you are ready, write Trigonometry Test. Find the unknown side or angle in each of the following diagrams: Sometimes more than one technique from the formula table at the top of this page can be used to solve a trig problem, but you will want to choose the most efficient and easiest method to save time. Finding Sides Example Work out the length of x in the diagram below:

These examples illustrate the decision-making process for a variety of triangles: You are commenting using your Twitter account. We do know a side and its opposite angle. The triangle to the right of the dotted line is right-angled, so use the appropriate trig ratio sin, cos or tan. Formulae You Should Know You should already know each of the following formulae: Use sine law to write an equation in sin B.

Solve the resulting equation to find the sine of the unknown angle: You are commenting using your Google account.

# Section 4: Sine And Cosine Rule

Sine Rule The Sine Rule can be used in any triangle not just right-angled triangles where a side and its opposite angle are known.

The only formula above which is in the A Level Maths formula book is the one highlighted in yellow. Points A, B cpsines C are in the same vertical plane.

The flowchart below shows how to decide which method to use:. The triangle is right-angled. A tutorial with problems, detailed solutions and exercises with answers. The triangle is not right-angled, but we do know a side and its opposite fosines, so we use the Sine Rule.

Twitter Facebook Like this: Geometry Tutorials, Problems and Interactive Applets.

After finding x you have enough information to use trigonometry in the right-angled triangle above the dotted line. Solving Problems involving right triangles Solving problem involving more than one right triangle.

Use the Sine Rule to find unknown sides and angles Use the Cosine Rule to find unknown sides and angles Combine trigonometry skills to solve problems Each topic is introduced with a theory section including examples and then some practice questions. Fill in your details below or click an icon to log in: Sometimes more than one technique from the formula table at the top of this lwa can be used to solve a trig problem, th you will want to choose the most efficient and easiest method to save time.

Leave a Reply Cancel reply Enter your comment here The triangle to the right of the dotted line is right-angled, so use the appropriate trig ratio sin, cos or tan.

Start by writing out the Cosine Rule formula siens finding angles: Explain the steps in a given proof of the sine law or cosine law. Pge required Address never made public.

Fill in the values you know, and the unknown angle: If you found any problems or would like to add any comments, please fill out the form below and click on the send button. You are commenting using your WordPress.

## Solving Triangles – using Law of Sine and Law of Cosine

The triangle is right-angled, but the question does not involve angles, so we need to use Pythagoras’s Theorem. Solve a problem involving the cosine law that requires the manipulation of a formula. We are particularly interested in mathematical errors or aspects of the page which could be confusing. You are allowed to use calculators in this topic.

## Sine Law to Solve Triangle Problems

Finding Sides If you need to find the laww of a side, you need to know the other two sides and the opposite angle. Solve problems that involve the cosine law and the sine law, including the ambiguous case. Draw a diagram to represent a problem that involves the cosine law or sine law.

The question does not involve angles. The triangle is not right-angled.

The ambiguous case of the sine law, where two sides and one angle are given, is also considered problems 3 and 4. Solution to Problem 4 Use sine law to write an equation in sin B.

These examples illustrate the decision-making process for a variety pagge triangles: Step 1 Start by writing out the Cosine Rule formula for finding angles: