# When is the cosine positive?

Question by: Kayla Conte | Last updated: September 20, 2021

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– the cosine is positive if the angle lies in the first or fourth quadrant, negative in the second or third quadrant.

## When is the cosine of an angle positive?

c In the first quadrant [ figura c] the cosine is positive, because the abscissa of B is positive. As the angle increases, the cosine value decreases; when α = 90 ° the cosine is zero. … The abscissa of point B is called the cosine of the angle α. In practice, the cosine of an angle varies between –1 and +1, including extremes.

## When is breast positive?

The graph of the sine function is called sinusoid while that of the cosine is called cosine. From these graphs it can be seen that the sine is positive in the I and II quadrant of the Cartesian plane while it is negative in the III and IV quadrant. The cosine is positive in the I and IV quadrant while it is negative in the II and III quadrant.

## What is the first fundamental relationship of Goniometry?

The sum of the squares of the sine and cosine of the same angle is equal to unity. This is the first fundamental relationship of goniometry.

## What are the sine and cosine values?

Sine and cosine, indicated by sin (α) and cos (α), are two fundamental trigonometric functions which are defined starting from the goniometric circumference, and which associate a certain numerical value between -1 and +1 to each angle.

## Find 17 related questions

### When is sine equal to 1?

What values ​​does the breast assume? … The sine is equal to 0 when the angle α is 0 ° or 180 °. The sine is equal to 1 when the angle α is 90 ° The sine is equal to -1 when the angle α is 270 °.

### How to calculate an angle with sine and cosine?

Calculate the angle with the calculator

1. To calculate an angle from the sine just press the sin-1 button, that is the arcsine function.
2. To calculate an angle from the cosine just press the cos-1 button, i.e. the arccosine function.

### What does the second fundamental relation of Goniometry say?

Second relation of goniometry

The triangles POH and TOA are similar in that they have the same congruent angles, therefore corresponding sides are proportional.

### What is the second fundamental relationship of Goniometry?

The second fundamental relation of goniometry is tg α = sin α cos α tg \ alpha = \ frac {sin \ \ alpha} {cos \ \ alpha} tgα = cos αsen α. The proof is linked to the calculation of the angular coefficient of the straight line on which the second side of the angle α lies.

### What are the fundamental relationships of Goniometry?

Fundamental relationships of goniometry

• sin 2 α + cos 2 α = 1.
• tan α = sin α cos α

### Where are the breasts positive and negative?

More precisely: – the sine is positive if the angle lies in the first or second quadrant, negative in the third or fourth quadrant; – the cosine is positive if the angle lies in the first or fourth quadrant, negative in the second or third quadrant.

### When is sine function negative?

As the third quadrant increases from 180 ° to 270 °, the sine decreases from 0 to -1 and is negative, while the cosine increases from -1 to 0 and is negative. As it increases from 270 ° to 360 °, in the fourth quadrant, the sine grows from – 1 to 0 and is negative, while the cosine grows from 0 to 1 and is positive.

### When is sine greater than or equal to zero?

I repeat: look at the circumference. The sine is greater than zero if the angle is between 0 and lazy!

### What is the cosine of 30 degrees worth?

Trigonometry Examples

The exact value of cos (30 °) cos (30 °) is √32.

### How to calculate the cosine of an angle?

The cosine trigonometric function, like sine and tangent, is based on the right triangle (a triangle containing an angle of 90 °). During math class, the cosine of an angle is found by dividing the length of the side adjacent to the angle by the length of the hypotenuse.

### How does the cosine of an angle vary?

Cosine

1. for values ​​between 0º and 90º the cosine of the point decreases;
2. for values ​​between 90º and 180º the cosine of the point decreases;
3. for values ​​between 180º and 270º the cosine of the point increases;
4. for values ​​between 270º and 360º the cosine of the point increases.

### How are the associated angles calculated?

Definition of associated angles

The arcs AB, AC, AD and AE, having amplitude respectively equal to α, 180 ° -α, 180 ° + α, 360 ° -α are called associated angles (or associated arcs) and have the values ​​of sine, cosine, tangent and cotangent equal in absolute value.

### How do you get the breast from the cotangent?

Therefore, it is perhaps easier for the lazy to learn the final formula directly, namely: the sine of the angle is equal to plus or minus (depending on the geometric quadrant) 1 divided by the root of 1 plus the value of the cotangent squared by angle.

### When is the Tan worth?

The tangent of 0, which from here on we will denote tan (0), is zero. To calculate the value of the tangent of zero we can use the definition of tangent, or we can use the goniometric circumference.

### Where does the cotangent not exist?

It is immediate to verify that, if the second side of the angle α falls on the x axis, that is, if α = 0 ° = 360 ° or α = 180 °, then there will be no intersection point between the line c and the second side angle. Therefore, for α = 0 ° (or for α = 360 °) and for α = 180 ° no cotangent value is defined.

### How are elementary goniometric equations solved?

To solve the elementary equations with the tangent it is necessary to find that angle whose tangent is equal to p. Since the tgx is a periodic function – that is, it repeats itself – every 180 °, then the result will be valid for every kπ.

### How do you calculate the tangent?

The tangent of an angle θ is equal to the ratio of the cosine to the sine of the same angle. The tangent of an angle θ is equal to the cotangent of the angle π / 2-θ measured in radians.

### How do you calculate the sine of an unknown angle?

Use the mathematical method

For example, if you want to know the sine of 150 °, an unknown angle, you can calculate it with the addition formula, expressing it as a sine of 90 ° + 60 °, known angle of which you know the value.

### How to find the sine and cosine of an angle without a calculator?

= RP / OP. Since the hypotenuse is equal to 1 in a goniometric circumference, by definition, the sine corresponds to the measurement of the cathetus opposite the angle. Similarly, the cosine will be the projection of P on the abscissa.