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Cos inverse formula is used to find the angle if hypotenuse, as well as base, are given. Inverses are used in trigonometric functions. All the inverse functions also possess some of the properties regarding the range and its domain name. Trigonometry functions are used to find the relation between right-angled triangle sides and the angle that is opposite to them. The ratios of the trigonometric in the verse are studied for finding out the value of an angle. These values can be found after the determination of the value of the adjacent sides. Here we are going to explain the Cos inverse formula along with some important questions.
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Keywords: Cos inverse Formula, the value of Cos inverse, trigonometric functions, anti-trigonometric functions, Derivative of Cos Inverse.
Also read: Isosceles Triangle Theorems
What is the Cos Inverse X?
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The Cos inverse formula is the inverse of Cos X. The meaning of Cos X is the value of an undetermined angle X. The value of the angle X represents the ratio between the base and hypotenuse of a triangle that is angled in the right direction. To represent it we used to write it as Cos X. The Cos inverse can also be written as Arccos & Cos-1. It is one of the 6 Inverse trigonometric functions.
Let’s considered this expression, so the inverse of the cosine of X is represented as Cos-1 so that is how we write the inverse of Cos. Moving on, let’s know how we can write it into the theoretical part of the trigonometric functions.
Cos X = adjacent side/Hypotenuse
Therefore, Cos -1 (adjacent side/ Hypotenuse) = X
So it is clear that it is represented in degrees.
The Cos formula is generated & now we can use it in the restricted domains.
Now it is easy to identify the formula of any ratios.
Cos Inverse X Formula
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The formula of Cos Inverse is explained as follows:
| Cos x = Adjacent/Hypotenuse |
| Cos -1 (Adjacent/Hypotenuse) = x |
| Cos -1 (-x) π - Cos -1 x Cos -1 x = π - Sin-1 1-x2, X<0 Cos -1 x = Sin -1 1-x2, x>0 |
What is the Value of Cos Inverse?
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The value of Cos inverse for Cos 1 degrees is the angle 1° that lies between 0° & 90° (first quadrant). The cosine function is positive in the first quadrant so the Cos 1° value is 0.9998476.
The Cosine function is a periodic function that we will represent as Cos 1°.
Cos 1 degrees = cos (1° + n × 360°), n € Z.
Read more: Multiplication Theorem on Probability
What are the Trigonometric functions?
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The trigonometric functions are also called the arcus functions or can be called anti-trigonometric functions. These functions are determined for finding the value of the angles. To find out the angles we consider the ratio of sides in a right-angled triangle. These are the inverse trigonometric functions and they are used in so many different fields like mathematics, Physics & engineering, etc.
These functions are divided into 6 parts:
- Sine (sin)
- Cosine (cos)
- Tangent (tan)
- Secant (sec)
- Cosecant (csc)
- Cotangent (cot)
Here we are reading about the Cosine (cos) function.
Read more: Probability distribution
Derivative of Cos Inverse Formula
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The first thing, we need to know about the derivation of Cos inverse is that it is the negative of the derivative of the sin inverse. The derivative of the cos inverse X delivers the rate of change in the inverse trigonometric function arccos x & it is given by
d(cos -1x)/dx=-1/√(1-x2)
Where -1<X<1
It is the same as the derivative of arccos that is written as
d(arccos)/dx=-1/1-x2
-1<X<1
Now we will determine the derivative of cos inverse with some of the methods.
So the formula for the derivative of Cos inverse X is
\(\frac{d}{dx}\) (cos-1X) = -\(\frac{1}{\sqrt {1-X^2}}\)
Where, -1<X<1
Derivative of Cos Inverse by the First principle
So here we are going to use the definition of limits, it is the first principle of differentiation.
Here we are going to use some different formulas for trigonometry limit and differentiation;
- f’(x)=lim h->0 f(x+h)-f(x)/h
- cos -1x + sin-1x = π/2
Derivative of Cos Inverse X with Sin Inverse X
We are going to find the derivative of Cos inverse x concerning the sin inverse x.
So here we have
- d(cos -1x)/dx=-1/√(1-x2)
- d(sin -1)/dx=1/√(1-x 2) => dx/d(sin -1x)=√(1-x 2)
So here we need to determine the value of d(cos -1x/d(sin-1x)
d(cos-1x)/d(sin-1x)=[d(cos-1x)/dx]/[d(sin -1x)/dx]
= [d(cos-1x)/dx] × dx/d(sin -1x)
=[-1/√(1 - x2)] × √(1-x 2)
= -1
So it is clear that the derivative of Cos inverse x concerning sin inverse X is -1.
Read more: Section Formula in Coordinate Geometry
Importance of Cos Inverse Formula
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The Cos inverse formula is important for every student of mathematics as it is one of the most important formulas of mathematics. To learn it more properly you must know why it is important?
Some points will help you to know it in a better way.
- The cos inverse formula will help you to determine the functions in all the fields. You will get to know how to use the formulas.
- The cos inverse formula will help you to learn the applications of the formula in different fields for different purposes.
- With the help of cos inverse, you will get to understand the outcome of the differentiation of cos inverse.
- The application of the trigonometric inverse function we used in all the scientific fields for many purposes.
- If you concentrate on understanding the formula properly then it will be easy for you to determine the output of any mathematical operation & you can solve it using the formula.
- The cos inverse is one of the best ways to find the value of the angles with the ratio of sides in a right-angled triangle.
- The inverse trigonometric functions are used in several different fields like engineering, physics & geometry, etc.
Read more: Independent Events in Probability
Things to Remember
- The cos inverse x formula is one of the trigonometric inverse functions. The total number of inverse trigonometric functions is six. The trigonometric functions are also called the anti- trigonometric functions. The derivative of the cos inverse x formula is the negative version of the derivative is of the sin inverse x formula.
- The six inverse trigonometric functions are the sine function, the cosine or arccosine inverse function, the arctangent tangent inverse function, the cotangent inverse function, the arcsecant inverse function and the covenant inverse function. These are represented as sine, cos, tan, cot, sec and cosec. These all are the six inverse trigonometric functions.
- The cos inverse is also called inverse cosine is used to determine the measurement of the angles using the value of the trigonometric ratio cos x. The inverse functions are determined to find the value of the angles and we will consider the ratio of the sides in a right-angled triangle. These functions are used in various fields.
- Cos-1x is the most decreasing function in its domain and it is neither an odd nor even function. This function is bounded in [0,π]. It is a periodic function. The maximum value of cos-1 x = π, occurs at x = 1. The minimum value of cos-1 x = 0, occurs at X= 1.
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Solved Questions
Ques: Determine the value of x if cos-1 (√4/2) = x using the inverse cosine formula. (2 marks)
Ans: As given in the question
We have, X = Adjacent sides/Hypotenuse
As we know that the Cos-1 x is an inverse function of cos x.
Then,
Cos (π/8) = √4/2
Since π/8 € [0,π], cos-1 (√4/2) = π/8
So, the value of x is π/8.
Ques: Find out the value of x if cos -1 (√3/3)= x using the inverse cosine formula. (3 marks)
Ans: As per the question,
Cos x = Adjacent sides/Hypotenuse
Cos -1 is an inverse function of cos x
As we know,
Cos (π/9) = √3/3.
Since π/9 €[0,π], cos-1 (√3/3) = π/9
So, The value of x is π/9.
Ques: Find cos -1 if ( -1/2). (2 marks)
Ans: as we know that
Cos -1 (-x) = cos-1 x
Hence, cos-1(-1/2)=π-cos-1 ½
= π – π/3
= 2π/3
So the cos-1 is 2π/3.
Ques: If the value of the base is √3, the hypotenuse is 3. Then find the value of angle a? (2 marks)
Ans: to find the angle a using the cosine inverse formula.
We need to calculate it as per the formula.
So, a = cos-1(base/hypotenuse)
a= cos -1 (√3/3)
a= π/9
So the angle a is π/9.
Ques: if (cos-1 5π/2) is given then solve it. (2 marks)
Ans: As we know,
Cos (cos-1) x = x,
Hence, cos (cos -1 5π/2)
= 5π/2
So the answer is 5π/2.
Ques: Solve Cos – 12/2 (1 mark)
Ans: cos – 12/2
. = π/6.
The answer will be π/6.
Ques: What is inverse cosine? (2 marks)
Ans: the inverse cosine is an import function of the inverse trigonometric functions. It is an inverse function of the cosine function. The inverse x is also written as arccos x. The inverse cosine functions are used to determine the measure of angles. It is done by using the value of the trigonometric ratio of the cos x. But we should remember one thing inverse cosine is not the reciprocal of cos x.
Ques: What are the properties of Cos inverse? (2 marks)
Ans: The properties of cos inverse are:
| Function | Range | Domain |
|---|---|---|
| Cos -1 | [-1, 1] | [0, π] |
Ques: What is the formula for Cos X inverse? (1 mark)
Ans: The formula for cos x inverse is;
Cos -1 x= adjacent sides/hypotenuse
Ques: Why it is essential to study trigonometric functions? (2 marks)
Ans: Trigonometric functions are important for all the students of Mathematics. You should know each & every formula that is useful to you. Trigonometric functions play a vital role in it, these functions are inverse trigonometric functions that have six parts & include six different formulas. It is essential to study trigonometric function because by studying about these inverses are used in various fields & you must know about all the uses of these functions.
Ques: Write the derivative of cos inverse x formula. (1 mark)
Ans: The derivative of cos inverse x formula is;
\(\frac{d}{dx}\) (cos -1 x) = -1/√(1-x2)
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