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Sin Cos Formulas
The Sin Cos Formulas, which relate to the angles and side ratios of a rightangled triangle, are the fundamental trigonometric functions. The ratio of the adjacent side to the hypotenuse is known as the cosine of an angle, and the sine of an angle is the ratio of the opposite side to the hypotenuse. These establish the fundamental identifies for sharp angles. The trigonometric function is the extension of these ratios to any angle in terms of radian measure. In the first and second quadrants, sin is positive, whereas the first and fourth quadrants of cos are positive. Under the real number domain, the Sin Cos Formulas have a range of [1,1].
Quick Links
ToggleThe notes and solutions to questions centred on the Sin Cos Formulas by Extramarks are also available in Hindi on the Extramarks website and mobile application.
The notes and solutions of the Sin Cos Formulas are all in accordance with the NCERT syllabus, therefore eliminating any chance of error. The notes and solutions of the Sin Cos Formulas have been prepared after consideration of past years’ question papers, therefore, students can estimate what kind of questions they might get to see in the examinations.
What Are Sin Cos Formulas?
The Pythagorean theorem states that x2 + y2 = 1, where x and y are the lengths of the rightangled triangle’s legs, holds true if (x, y) is a point on the unit circle and a ray from the origin (0, 0) to (x, y) forms an angle of from the positive axis. As a result, cos2 + sin2 = 1 replaces the original Sin Cos Formulas. In trigonometry, the Sin Cos Formulas are used to calculate angles and side ratios of rightangled triangles.
The Extramarks experts designed Sin Cos Formulas notes and solutions has a very simple yet powerful framework that is extremely easy to understand and very studentfriendly. Students should thus sign themselves up and enjoy unlimited access to the notes and solutions for the Sin Cos Formulas and so much more.
The Sin Cos Formulas that are used in trigonometric functions have various applications. These trigonometric formulae make it easier to assess all trigonometric expressions. Students can go through them in more depth on the Extramarks website and mobile application.
Sin Cos Formulas
The roles of negative angles are: for any sharp angle of;
 sin() equals – sin
 cos () equals cos
Trigonometry function identities expressed in terms of their complements:
 cos = sin(90°)
 cos(90° ) = sin
The Sin Cos Formulas notes and solutions offer stepbystep explanations throughout the notes to ensure that students actually understand and comprehend the content. The notes for Sin Cos Formulas are also downloadable to ensure that students can learn what they need to without any other disturbance and hassle.
The notes and solutions for Sin Cos Formulas have been compiled in collaboration with the top experts at Extramarks. Therefore, inaccuracy isn’t even a question when it comes to the authenticity of the notes.
Sum and Difference of Sin Cos Formulas
Compound angles are those formed by adding or subtracting two or more other angles. The compound angles are written by students as and. There are Sin Cos Formulas for extending or condensing trigonometric expressions with regard to compound angles. Students can go through the same on the Extramarks website and mobile application.
 sin (α + β) = sin α cos β + cos α sin β
 sin (α – β) = sin α cos β – cos α sin β
 cos (α + β) = cos α cos β – sin α sin β
 cos (α – β) = cos α cos β + sin α sin β
The Sin Cos Formulas notes and solutions are extremely helpful from an exam perspective. Mathematics can be very confusing, but with the right kind of resources and sheer practice and dedication, students can achieve almost anything. The study materials for Sin Cos Formulas have been made available on the Extramarks website and mobile application in both Hindi and English language.
Students from other boards can also refer to the Sin Cos Formulas notes and solutions.
Transformation of Sin Cos Formulas
students should choose a few identities from one side to use, and then substitute others until the side is changed into the opposite side. Rewrite either side of the equation and translate it to the other side in order to confirm a person’s identification. Get the producttosum and sumtoproduct formulae from the aforementioned sum and difference identities.
When given a product of cosines, producttosum formulae are used. Students must write the formula, replace the provided angles, and then simplify the product as a sum or difference.
 2 sin α cos β = sin (α +β) + sin (α – β)
 2 cos α sin β = sin (α + β) – sin (α – β)
 2 cos α cos β = cos (α + β) + cos (α – β)
 2 sin α sin β = cos (α – β) – cos (α + β)
Sums of sine or cosine can be expressed as products using the sumtoproduct formulas. The formulas for these are as follows:
 sin α + sin β = 2 sin((α+β)/2) cos((α−β)/2)
 sin α – sin β = 2 cos((α+β)/2) sin((α−β)/2)
 cos α + cos β= 2 cos((α+β)/2) cos((α−β)/2)
 cos α – cos β = 2 sin((α+β)/2) sin((αβ)/2)
Designed by Extramarks experts, Sin Cos Formulas notes and solutions provide a very simple yet powerful framework that is extremely easy to understand and studentfriendly.
Derivation of Product to Sum Formulas
Here, the sum of the cosine and sine products are used. The sum and difference identities for cosine allow us to construct the producttosum formula. The result of combining the two equations is cos cos + sin sin = cos( ) + cos cos sin sin = cosα cosβ + sinα sinβ = cos(α − β)
+ cosα cosβ − sinα sinβ = cos(α + β)
––—————————––————
2
cosα cosβ = cos(α−β) + cos(α + β)
Divide the result by 2, then find the product of cosines: cos cos equals (1/2) [cos(α−β) + cos(α+β)]
Similarly, by expressing the products as the sum/difference, students may get the other formulae.
Derivation of Sum to Product Formulas
There are several issues that call for the product’s reverse to sum. Let’s examine how these sumtoproduct formulae were developed. Students should utilize the replacements (u+v)/2 = and (uv)/2 = for this.
After that, u – u = [(u + v)/2] u – u = [(u + v)/2] – [(u v)/2] = v
They should then calculate the formula for the sum to the product. In the producttosum formula, swap out and think about
(sinα cosβ) = (1/2)[sin(α + β) + sin(α – β)]
Substituting for (α + β) and αβ, we get
sin((u+v)/2) cos ((uv)/2) = 1/2[sinu + sin v]
2sin((u+v)/2)) cos ((uv)/2) = sinu + sin v
The additional identities for sumtoproduct may be derived in a similar manner.
Sin Cos Formulas of Multiple Angles
The double and triple angles formula and the halfangle formulas as follows:
 sin 2θ = 2 sinθ cosθ
 sin 3θ = 3 sinθ – 4 sin3θ
 cos 2θ = cos2 θ – sin2 θ
 cos 2θ = 2cos2θ – 1
 cos 2θ = 1 2sin2 θ
 cos 3θ = 4 cos3θ – 3cosθ
 sin (θ/2) = ± √((1 cosθ)/2)
 cos (θ/2) = ± √((1+ cosθ)/2)
 sin θ = 2tan (θ/2) /(1 + tan2 (θ/2))
 cos θ = (1tan2 (θ/2))/(1 + tan2 (θ/2))
Examples Using Sin Cos Formulas
Example 1:
If sin X = 1/2 and cos Y = 3/4 find cos(X+Y)
Solution: We know cos(X + Y) = cos X cos Y – sin X sin Y
Given sin X = 1/2
We know that, cos X = √(1 – sin2X) = √(1 – (1/4)) = √3/2
Thus, cos X = √3/2
Given cos Y = 3/4
We know that, sin Y = √(1 – cos2Y) = √(1 – (9/16)) = √7/4
Thus, sin Y = √7/4
cos X = √3/2, and sinY = √7/4
Applying the sum of cos formula, we have cos(X+Y) = (√3/2) × (3/4) – 1/2 × (√7/4)
= (3√3 – √7)/8
Answer: cos(X+Y) = (3√3 – √7)/8
Example 2: If sin θ = 3/5, find sin2θ.
Solution: We know that sin2θ = 2 sin θ cos θ
We need to determine cos θ.
Let us use the sin cos formula cos2θ + sin2θ = 1.
Rewriting, we get cos2θ = 1 – sin2θ
= 1(9/25)
cos2θ = 16/25
cos θ = 4/5
sin2θ = 2 sin θ cos θ
= 2 × (3/5) × (4/5) = 24/25
Answer: sin2θ = 24/25
FAQs (Frequently Asked Questions)
1. What do Sin Cos Formulas mean?
The hypotenuse and the two legs of a rightangled triangle are the adjacent and the opposite sides, respectively. The trigonometric ratios are therefore presented as cos = adjacent and sin = opposite and hypotenuse, respectively. Students can estimate what types of questions they might encounter in the examinations by referring to the notes and solutions of the Sin Cos Formulas prepared based on past years’ question papers.
2. How can one separate Cos from Sin?
Sine is the opposing side or hypotenuse in every rightangled triangle. As a result of knowing these two sides, the adjacent side—also known as the hypotenuse—is discovered and applied in the cosine formula. To ensure that students actually understand and comprehend the content, the Sin Cos Formulas notes and solutions provide stepbystep explanations throughout.