# When to use law of sines

## How do you know when to use the law of sines or cosines?

The sine rule is used when we are given either a) two angles and one side, or b) two sides and a non-included angle. The cosine rule is used when we are given either a) three sides or b) two sides and the included angle.

## When would you use the sine function?

The Sine Function

This ratio can be used to solve problems involving distance or height, or if you need to know an angle measure. Example: Imagine a ship that is tethered to an anchor on the ocean floor. The anchor’s chain is 30 m long and creates a line that is the hypotenuse of a right triangle.

## Can you use law of sines for SSS?

Use the law of cosines when you are given SAS, or SSS, quantities. For example: If you were given the lengths of sides b and c, and the measure of angle A, this would be SAS. SSS is when we know the lengths of the three sides a, b, and c. Use the law of sines when you are given ASA, SSA, or AAS.

## Can you use the law of sines on any triangle?

The Sine Rule can be used in any triangle (not just right-angled triangles) where a side and its opposite angle are known. You will only ever need two parts of the Sine Rule formula, not all three.

## Can you use law of cosines on right triangles?

You can ONLY use the Pythagorean Theorem when dealing with a right triangle. The law of cosines allows us to find angle (or side length) measurements for triangles other than right triangles. The third side in the example given would ONLY = 15 if the angle between the two sides was 90 degrees.

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## What does a sine curve look like?

To graph the sine function, we mark the angle along the horizontal x axis, and for each angle, we put the sine of that angle on the vertical y-axis. The result, as seen above, is a smooth curve that varies from +1 to -1. … This shape is also called a sine wave, especially when it appears in radio and electronic circuits.

## Why Sine is called sine?

The word “sine” (Latin “sinus”) comes from a Latin mistranslation by Robert of Chester of the Arabic jiba, which is a transliteration of the Sanskrit word for half the chord, jya-ardha.

## How is sine calculated?

The sine function, along with cosine and tangent, is one of the three most common trigonometric functions. In any right triangle, the sine of an angle x is the length of the opposite side (O) divided by the length of the hypotenuse (H). … Use your calculator to find the sine of 30°.

## How do you use the law of cosines?

When to Use

The Law of Cosines is useful for finding: the third side of a triangle when we know two sides and the angle between them (like the example above) the angles of a triangle when we know all three sides (as in the following example)

## Is Asa law of sines?

“ASA” is when we know two angles and a side between the angles. then use The Law of Sines to find each of the other two sides.

## How do you use the law of cosines in SSS?

To solve an SSS triangle:

1. use The Law of Cosines first to calculate one of the angles.
2. then use The Law of Cosines again to find another angle.
3. and finally use angles of a triangle add to 180° to find the last angle.
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## What is the law of sines and cosines?

The Law of Sines establishes a relationship between the angles and the side lengths of ΔABC: a/sin(A) = b/sin(B) = c/sin(C). Another important relationship between the side lengths and the angles of a triangle is expressed by the Law of Cosines. …

## What is sine law of Triangle?

The law of sines can be used to compute the remaining sides of a triangle when two angles and a side are known—a technique known as triangulation. … The law of sines is one of two trigonometric equations commonly applied to find lengths and angles in scalene triangles, with the other being the law of cosines.