Can the law of cosines only be applied to acute angles?

No, the Law of Cosines can be applied to any triangle, including acute, right, and obtuse triangles; it's a universal formula, not limited to acute angles, and works because the cosine function correctly handles angles greater than 90 degrees (obtuse) by giving negative values, which accurately adjust the formula. It's a fundamental relationship in geometry that holds true for all triangles.

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Does cosine law work for obtuse angles?

The sine law and cosine law can be used to determine unknown side lengths and angle measures in obtuse triangles. The sine law and cosine law are used with obtuse triangles in the same way that they are used with acute triangles.

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Does the law of cosines apply to all triangles?

Yes, the laws apply to right-angled triangles as well. But, they're not particularly interesting there: For △ABC with θ=∠ABC a right angle, we can try to apply the cosine law about the right angle, and get AC2=AB2+BC2−AB⋅BC⋅cosθ=AB2+BC2, as cos90∘ = 0.

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What is the law of cosines for non right angles?

The Law of Cosines states that the square of any side of a triangle is equal to the sum of the squares of the other two sides minus twice the product of the other two sides and the cosine of the included angle.

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What are the limitations of the law of cosines?

Dependence on Accurate Measurements: The accuracy of the results obtained using the Law of Cosines is highly dependent on the precision of the measurements of the sides and angles. Any errors in these measurements can lead to significant discrepancies in the calculated values.

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Proof of the cosine rule

31 related questions found

When can you not use cosine law?

To solve a triangle is to find the lengths of each of its sides and all its angles. 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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Does Soh Cah Toa apply to all triangles?

For right-angled triangles, we have Pythagoras' Theorem and SOHCAHTOA. However, these methods do not work for non-right angled triangles. For non-right angled triangles, we have the cosine rule, the sine rule and a new expression for finding area.

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Is the cosine rule only for right-angled triangles?

The Cosine Rule can be used in any triangle where you are trying to relate all three sides to one angle.

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Does cos repeat every 180 or 360?

Cosine is a periodic function that repeats every 360°.

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Is trig harder than calculus?

In general, calculus is considered to be more difficult than trigonometry due to the complexity of the concepts. However, the difficulty level can also depend on your personal strengths, interests, and previous experience with math courses.

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What is the 30-60-90 rule for triangles?

The side opposite the 60-degree angle is the longer leg. The hypotenuse is twice the length of the shorter leg. The longer leg is the square root of 3 times the shorter leg. The area of a 30-60-90 triangle is one-half times the square root of 3 times the length of the shorter side squared.

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Does the law of cosines work for all triangles?

The Pythagorean Theorem can be used only for the right-angled triangles. But the law of cosines is applicable to all triangles. Pythagorean theorem: The Pythagorean theorem states that the sum of squares of the lengths of the two short sides of the right triangle is equal to the square of the length of the hypotenuse.

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What cannot be the cosine of an angle?

The cosine of an angle cannot be outside of the range from -1 to 1. Recall the definition of the cosine of an angle. It is the ratio of the adjacent side to the hypotenuse. This ratio can never exceed 1, and can never be below -1.

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Is an obtuse angle always 90?

Obtuse angles are always between 90 and 180 degrees. The obtuse angle degree range must always be greater than 90 and less than 180. Obtuse angles take up between a quarter and a half of a circle. Note that obtuse angles are specifically defined as between 90 and 180 degrees.

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Why is sin 270 =- 1?

The value of sin 270 degrees can be calculated by constructing an angle of 270° with the x-axis, and then finding the coordinates of the corresponding point (0, -1) on the unit circle. The value of sin 270° is equal to the y-coordinate (-1). ∴ sin 270° = -1.

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Why is 180 π?

The value of 180 degrees in radians is π. Because 2π = 360 degrees. When we divide both sides by 2, we get π = 180 degrees.

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What are sine, cosine, and tangent used for?

Understanding Sin Cos Tan

Using these three ratios, you can solve many problems involving right-angled triangles, such as finding the height of an object, calculating angles and measuring distances. These functions may seem abstract, but they are necessary in different professions.

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Do cos and sin only work for right triangles?

Sine, cosine, and tangent can only be used on right triangles. However, any triangle can be divided into two right triangles, and then solved.

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Is a right triangle always 45 45 90?

The statement 'An isosceles right triangle is always a 45-45-90 triangle' is true. An isosceles right triangle has two sides that are equal in length, and one right angle (90 degrees). The angles in any triangle must sum up to 180 degrees. Thus, the two equal angles are both 45 degrees.

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Does Soh Cah Toa apply to non-right triangles?

SOHCAHTOA requires all angles to be equal. SOHCAHTOA only applies to right triangles.

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Why is 14 48 50 not a Pythagorean triplet?

Final Answer

Yes, the numbers 14, 48, 50 form a Pythagorean triplet because 142+482=502.

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Does a 2 b 2 c 2 only apply to right triangles?

Say that, for any triangle with the property a^2+b^2=c^2, you can create a right triangle that is congruent to it, and therefore, the original triangle would be a right triangle. Edit: Also, the converse of the pythagorean theorem is true, so there is no non-right triangle where a^2+b^2=c^2.

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How do I know if I should use Soh Cah or Toa?

Use SOH CAH TOA in right-angled triangles to find unknown sides or angles by remembering the trigonometric ratios: Sin = Opposite / Hypotenuse (SOH), Cos = Adjacent / Hypotenuse (CAH), and Tan = Opposite / Adjacent (TOA). Choose the formula that matches the sides you know and the side or angle you need to find.
 

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