# when to use law of sines or cosines

## Best answer

How do you know when to use 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.

## People also ask

### What is the difference between the law of sines and cosines?

Depending on the information we have available, we can use the law of sines or the law of cosines. The law of sines relates the length of one side to the sine of its angle and the law of cosines relates the length of two sides of the triangle to their intermediate angle.

### How do you use the law of sines in geometry?

The law of sines is used to solve triangles in which you know only two angles and one of the opposing sides (called AAS for angle-angle-side), or two sides and one of the opposing angles (called SSA for side-side-angle). Is SSS law of cosines? The Law of Cosines states that: Use the law of cosines when you are given SAS, or SSS, quantities.

### What is the law of cosines problem?

Since you know 2 sides, their included angle, and you are trying to find the side length opposite the angle, this is Law of Cosines problem. Decide which formula (Law of Sines/Cosines) you would use to calculate the value of x below?

### What is the included angle in the law of cosines?

Remember, the law of cosines is all about included angle (or knowing 3 sides and wanting to find an angle). In this case, we have a side of length 20 and of 13 and the included angle of 66 鈭?.