# when to use law of sines or cosines 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.

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• ### 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?.

# when to use law of sines and law of cosines How do you know when to use the law of sines or cosines? The sine rule is usedwhen 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 formula for the law of cosines?

• The formula for the law of cosines is an equation that relates the lengths of two sides of a triangle to the angle between the two sides. The formula for the law of cosines is: where, a, b, c represent the lengths of the sides of the triangle and 伪, 尾, 纬 represent the angles of the triangle as shown in the following image.

• ### How do you use the Pythagorean theorem with the law of cosines?

• 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.

# how to find an angle using law of cosines Law of Cosines for Angles A, B, and C: If you know three sides of a triangle then you can use the cosine rule to find the angles of a triangle. So, the solving formula for the angles which are used by the law of cosines formula is:A = cos鈭?[ b2 +c2 鈭抋2 2bc] A = c o s 鈭?1 [ b 2 +c 2 鈭?a 2 2 b c]

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• ### What is the law of cosines for angles A B C?

• Law of Cosines for Angles A, B, and C: If you know three sides of a triangle then you can use the cosine rule to find the angles of a triangle. So, the solving formula for the angles which are used by the law of cosines formula is: A = cos鈭?[ b2 +c2 鈭抋2 2bc] A = c o s 鈭?1 [ b 2 + c 2 鈭?a 2 2 b c]

• ### How do you find the unknown angles using cosine law?

• The formula to find the unknown angles using cosine law is given by: cos 伪 = [b 2 + c 2 鈥?a 2 ]/2bc cos 尾 = [a 2 + c 2 鈥?b 2 ]/2ac cos 纬 = [b 2 + a 2 鈥?c 2 ]/2ab

• ### How do you use the law of cosines to find length?

• In the last lesson we used the Law of Cosines to find the length of the third side of a triangle when you know the length of two sides and the angle in between. This law can also be used to find the measure of an angle when the three sides of a triangle are given. 1.

• ### How does the law of cosines work for right triangles?

• Remember that the Law of Cosines works for any triangle, not just right triangles. In the last lesson we used the Law of Cosines to find the length of the third side of a triangle when you know the length of two sides and the angle in between. This law can also be used to find the measure of an angle when the three sides of a triangle are given. 1.

# how to use law of cosines In the last lesson we used the Law of Cosines tofind the length of the third side of a triangle when you know the length of two sides and the angle in between. This law can also be used to find the measure of an angle when the three sides of a triangle are given. To use the Law of Cosines to find an unknown angle: 1.

## People also ask

• ### What is the law of cosines?

• The law of cosines is a formula that relates the three sides of a triangle to the cosine of a given angle. There are 2 cases for using the law of cosines.

• ### How do you use the law of cosines to solve a triangle?

• Because you know two sides of the triangle, along with the angle that is opposite your unknown side, you can use the law of cosines to help you calculate that third side: Let’s go ahead and solve this problem as our first example. We know two sides of the triangle. One measures 1 mile and the other measures 2 miles.

• ### How do surveyors use the law of cosines?

• Surveyors use triangles to calculate an unknown distance where they know the other two distances of the triangle. The beauty of the law of cosines can be seen when you want to find the location of a fire, for example. You see the fire in the distance, but you don’t know how far away it is.

• ### What is the difference between the law of cosines and hypotenuse?

• One more difference is that a, b, and c in the law of cosines all refer to different sides of a triangle. There’s no hypotenuse anymore since we are dealing with triangles of all kinds, not just right triangles. The big C inside the cosine argument stands for the angle opposite side c: Are you a student or a teacher?