CosA + cosB + cosC = 1 + 4sinA/2 sinB/2 sinC/2

1 answer:

6 0

$\cos(A) + \cos( B ) + \cos(C) \\ = 2 \cos( \frac{A + B}{2} ) \cos( \frac{ A- B}{2} ) + 1 - 2 { \sin }^{2} \frac{C}{2} \\ = 1 + 2\cos( \frac{\pi - C}{2} ) \cos( \frac{A - B}{2} ) - 2 { \sin }^{2} \frac{C}{2} \\ = 1 + 2 \sin \frac{C}{2} \cos( \frac{A - B}{2} ) - 2 { \sin }^{2} \frac{C}{2} \\ = 1 + 2 \sin \frac{C}{2} [ \cos( \frac{A - B}{2} ) - \sin \frac{C}{2}] \\ = 1 + 2 \sin \frac{C}{2} [ \cos( \frac{A - B}{2} ) - \cos( \frac{A + B}{2} )] \\ = 1 + 2 \sin\frac{C}{2} \times 2 \sin( \frac{ \frac{A + B}{2} +\frac{A - B}{2} }{2} ) \sin( \frac{ \frac{A + B}{2} - \frac{A - B}{2} }{2} ) \\ = 1 + 4 \sin \frac{A}{2} \sin \frac{B}{2} \sin \frac{C}{2}$

You might be interested in

In ΔDEF, the measure of ∠F=90°, DF = 24, FE = 7, and ED = 25. What ratio represents the sine of ∠E?

kumpel [21]

Answer:

24/25

Step-by-step explanation:

In this triangle DF and FE are legs (because they form the right angle) , ED is the hypotenuse (it is the largest side, it is opposite to the right angle).

son of E is the ratio of the leg opposite to the angle E (DF) to the hypotenuse

it is 24/25

4 0

3 years ago

A surveyor is studying a map of the community and is using vectors to determine the distance between two schools. On the map, th

guajiro [1.7K]

<h2>C. components: (-28,-25), actual distance about 37.54 meters</h2>

5 0

3 years ago

Read 2 more answers

Jackson buys a grape snow cone on a hot day. By the time he eats all the "snow" off the top, the paper cone is filled with 27\pi

anyanavicka [17]

Question:

Jackson buys a grape snow cone on a hot day. By the time he eats all the "snow" off the top, the paper cone is filled with 27\pi27π27, pi cm^3 3 start superscript, 3, end superscript of melted purple liquid. The radius of the cone is 333 cm. What is the height of the cone?

Answer:

The height of the cone is $9 \ cm$