When To Use Law Of Cosines?

When given SAS or SSS quantities, use the law of cosines. This would be SAS if you were given the lengths of sides b and c, as well as the measure of angle A. When we know the lengths of the three sides a, b, and c, we call it SSS.

Similarly, When should you use law of cosines?

To solve a triangle, you must determine the lengths of all of its sides and angles. When we are given a) two angles and one side, or b) two sides and a non-included angle, we utilize the sine rule. When we are provided either a) three sides or b) two sides and the included angle, we utilize the cosine rule.

Also, it is asked, What cases need to use law of cosines?

When Should You Use It? When we know two sides and the angle between them, we may apply the Law of Cosines to get the third side of a triangle (like the example above) When we know all three sides of a triangle, we may calculate its angles (as in the following example)

Secondly, When can the law of sines be used?

When we know two angles and one side or two angles and one included side, we usually utilize the law of sines to solve the triangle. When we have ASA (Angle-Side-Angle) or AAS (Angle-Angle-Side) criteria, the law of sines may be used.

Also, What is the difference between law of sines and law of cosines?

The sines of the angle and the side opposite it are related by the rule of sines. The angle opposing a side is also used in the law of cosines. With the proper set of inputs, they may both be used to calculate the length of a triangle’s side or one of its angles.

People also ask, In which of the following situation will the law of cosine be applied?

The Cosine Rule may be applied to any triangle in which all three sides must be related to one angle. You’ll need to know the other two sides as well as the opposite angle to calculate the length of a side.

Related Questions and Answers

Can the Law of Cosines be applied to right triangles?

Any triangle, not simply right triangles, may be used. where a and b are the two provided sides, C is their included angle, and c is the third side that is unknown. See the diagram above.

What 2 cases can the Law of Sines be used?

When Should the Law of Sines Be Used? When Angle-Side-Angle (ASA) or Angle-Angle-Side (AAS) congruency exists, the Law of Sines is applied. In fact, in our next lesson, titled the Ambiguous Case, we’ll learn about another form of congruency that the Law of Sines may be applied to.

Can you always use Law of Sines?

The law of sines formula enables us to calculate a percentage of opposing sides/angles (technically, you’re really taking the sine of an angle and its opposite side) When should the law of sines formula be used? What you’re aware ofWhat you’re able to locate 2 angles and the sideside opposite the known angle that is not included

Which case Cannot be solved using laws of sines?

We cannot utilize the Law of Sines if we are given two sides and an included angle of a triangle, or if we are given three sides of a triangle, since we cannot build up any proportions where adequate information is provided. In these two circumstances, the Law of Cosines must be applied.

Which of the following best describes the law of cosines?

The Law of Cosines is best described by which of the following phrases? The total of the squares of the remaining two sides, minus twice the product of the two remaining sides and the cosine of the angle between them, equals the square of any side of a triangle. You’ve only gone through 5 terms!

Why do we need sine and cosine?

It may assist us in better comprehending the relationships between rectangle sides and angles. In the study of right triangles, the terms sine, cosine, and tangent are crucial. Have you ever seen a triangle like this before? If that’s the case, you’re aware that one of the three angles is always 90 degrees (a right angle).

What is meant by cosine law?

The square of a side of a planar triangle is the total of the squares of the other sides minus twice the product of those sides and the cosine of the angle between them, according to the law of cosines 1.

Which law should be applied if three sides of a triangle are given?

SSS: If you know the three sides of a triangle, apply the Law of Cosines to determine one of the angles. It’s normally better to start with the greatest angle, which is the one on the opposite side of the longest side. Then, to get the second angle, build up a proportion using the Law of Sines.

In which of these cases can we use the law of sines to solve the triangle?

Applying the Law of Sines: As long as two of the angles and one of the sides are known, the Law of Sines may be used to solve for missing lengths or angle measurements in an oblique triangle.

Why can’t you solve this triangle using the law of sines?

Because we need to know at least one angle and the opposite side to solve an SAS triangle, we can’t utilize the Law of Sines in the first step.

Can you use law of sines on obtuse triangles?

The sine rule also applies to obtuse-angled triangles: = for an obtuse-angled triangle. To compute the sine and cosine of the angles 0°, 90°, and 180°, we may utilize the expanded definition of trigonometric functions.

Why does sine rule not work?

When the three sides of a triangle are known, the three angles may be calculated individually. (The SSS congruence test is used here.) We may use the cosine rule instead of the sine rule to calculate the three angles since the sine rule needs knowledge of (at least) one angle.

Can the law of cosines be used to solve any triangle for which two angles and a side are known explain your answer?

When the lengths of two sides and the measure of the included angle (SAS) or the lengths of the three sides (SSS) are known, the Law of Cosines is used to identify the remaining components of an oblique (non-right) triangle.

Is the Pythagorean theorem a special case of the law of cosines?

Because cos (theta) = 0 when the angle is a 90 degree or right angle, the Pythagorean Theorem is a specific instance of the law of cosines, a2 + b2 – 2*a*b*cos (theta) = c2. We also discovered that the Pythagorean Theorem’s inverse is correct.

Can you solve SSS with law of sines?

To solve a triangle, you must first determine all of the angles and side lengths. The Law of Sines is a useful technique for resolving triangles, but it requires the knowledge of an angle and its opposite side. As a result, the Law of Sines cannot be utilized to solve SSS (side-side-side) or SAS (side-angle-side) configurations as a first step.

Can you solve SAS with law of sines?

When we know two sides and the angle between them, we call it “SAS.” Calculate the unknown side using The Law of Cosines, then determine the lesser of the other two angles using The Law of Sines, and then add the three angles to 180° to obtain the last angle.

Which of the following cases where we can use the law of cosines in solving oblique triangles?

When two sides and their included angle are supplied, and when three sides are given, this rule is employed largely in two circumstances. When two sides and their included angles are known, the third side must be calculated. As illustrated above, the Law of Cosines is ideal for the circumstance.

Why do we need sine?

As we’ve seen, sine is one of the most important trigonometric functions, and it’s defined as the ratio of the opposite angle’s side divided by the hypotenuse. It’s useful for calculating distances and heights, and it can also be used to calculate angle measurements in radians.


The “when to use law of sines” is a trigonometric function that can be used in many different scenarios. The Law of Sines is best used when the side lengths are known.

This Video Should Help:

The “law of cosines to find angle” is a trigonometric equation that can be used to find the angle between two lines.

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