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Can the law of cosines be used to find a length or just angle?
Wiki User
∙ 10y ago
Either.
However, if you know two sides and the includedangle then the sine rule is simpler.
Wiki User
∙ 10y ago
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Law of cosines with a right angle?
The law of cosines with a right angle is just the pythagorean theorem. The cosine of 90 degrees is 0. That is why the hypotenuse squared is equal to the sum of both of the legs squared
How do you find the arc length when the central angle is given?
Well, in degrees, the arc is congruent to its central angle. If the radius is given, however, just find the circumference of the circle (C=πd). Then, take the measure of the central angle, and divide that by 360 degrees. Multiply the circumference by the dividend, and you will get the arc length. This works because it is a proportion. Circumference:Arc length::Total degrees in triangle:Arc's central angle. Hope that helped. :D
How long must a right triangle be?
It can be any length; a right angle triangle just needs to include a right angle somewhere. But length has nothing to do with whether it is a right angle or not.
Can side length of 6 9 and 10 make a triangle?
Yes, use the Law of Cosines: a2=b2+c2-2bc*cosA where a, b, c are the lengths of the sides and A is the angle opposite to a. Just plug in the three values and solve for cosA. The answer is 0.805555556 (if you make a=6) which is in the interval [-1,1] so it is in the range of cosA. Since there exists an angle A using those 3 inputs, they can form a triangle.
How do you find the length of a side opposite an angle?
You have not described this problem in sufficient detail. If you are talking about triangles, then in some situations trigonometric functions are applicable. Or, you could just measure the side with your ruler, although if that is what you are going to do, then the fact that it is oppoiste an angle is irrelevant.
Law of cosines with a right angle?
The law of cosines with a right angle is just the pythagorean theorem. The cosine of 90 degrees is 0. That is why the hypotenuse squared is equal to the sum of both of the legs squared
If you have all sides of a triangle how do you use the law of cosines to solve the angles?
Label the angles of the triangle A, B, and C. Label the side opposite angle A side a, the one opposite angle B side b, and the one opposite angle C side c. Let's say you want to solve for angle A, you use the law of cosines: a^2=b^2+c^2-2bcCosA CosA is the "variable" in this equation, so isolate this. When you have that, you'll have some number (let's call it D) equal to CosA: D=CosA Use the inverse Cos function to find the measure of the angle: Cos^-1(D)=A And you have the measure of angle A. From here you can either use the law of cosines again to find a second angle and then the third, though the easier route is usually to just use the law of sines for find the second angle and then the fact that all three angles add to 180 to find the third.
Does a angle have infinite length?
An angle has no length at all. The angle is just the amount of opening between the two lines where they meet. The length of the angle's sides is completely irrelevant, and has no effect at all on the measure of the angle. They can be any length from almost zero to infinite, and they don't even have to both be the same length. It just doesn't matter. None of that changes the measure of the angle.
How do you find the arc length when the central angle is given?
Well, in degrees, the arc is congruent to its central angle. If the radius is given, however, just find the circumference of the circle (C=πd). Then, take the measure of the central angle, and divide that by 360 degrees. Multiply the circumference by the dividend, and you will get the arc length. This works because it is a proportion. Circumference:Arc length::Total degrees in triangle:Arc's central angle. Hope that helped. :D
How find radius in a circle given angle and length of arc?
angle of arc/ angle of circle (360°) = length of the arc/ total circumference (2 pi* radius) so you just have to find r then so: angle of arc/ angle of circle (360°) *2pi = length of the arc/ radius radius= ength of the arc/ angle of arc/ angle of circle (360°) *2pi not that hard ;)
How long must a right triangle be?
It can be any length; a right angle triangle just needs to include a right angle somewhere. But length has nothing to do with whether it is a right angle or not.
Can side length of 6 9 and 10 make a triangle?
Yes, use the Law of Cosines: a2=b2+c2-2bc*cosA where a, b, c are the lengths of the sides and A is the angle opposite to a. Just plug in the three values and solve for cosA. The answer is 0.805555556 (if you make a=6) which is in the interval [-1,1] so it is in the range of cosA. Since there exists an angle A using those 3 inputs, they can form a triangle.
How do you find the length of one side if you have the others on a triangle?
If the triangle is a right triangle, where one angle is equal to 90o, Then you can use the Pythagorean Theorem. To use this, label each side of the right triangle a, b, and c, in which c is the hypotenuse/longest side/side opposite of the 90o angle; a2+b2=c2 . Just input the values into this equation and you are able to get one side as long as you know the other two. If the triangle is not a right triangle, then you would need to know an angle of one of the sides already known in order to use the law of cosines.
How do you figure the length of C on an open or closed angle?
Just Measure it
How do you find the length of a side opposite an angle?
You have not described this problem in sufficient detail. If you are talking about triangles, then in some situations trigonometric functions are applicable. Or, you could just measure the side with your ruler, although if that is what you are going to do, then the fact that it is oppoiste an angle is irrelevant.
How do you measure a vector?
Measuring a vector requires a reference. You'll need something that will allow you to find direction, and a unit length so you can find magnitude. A graph is a good way to do this, and something with a standard x and y axis (Cartesian coordinates) is just the ticket. Our graph has an origin, and that can be your starting point. Starting there, and using the x-axis as zero degrees, find your angle. Then draw a segment out along that axis the appropriate length. You now have a vector with its angle (direction) and length (magnitude).
How do you measure an obtuse angle?
You need to use a protractor. You can also calculate it from the length of the three sides of a triangle it would make. Since an obtuse angle lies between 90 and 180 degrees just draw a line bisecting the two angle lines and measure the length of each of the three resulting sides. View Wikipedia in the related link below to find out how to use trigonometry to accomplish this.
