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2 years ago

Prove that:cos20°cos40°cos80°=1/8

Mathematics

2 answers:

Naya [18.7K]2 years ago

7 0

Answer:

see explanation

Step-by-step explanation:

Using the double angle identity for sine

sin2x = 2sinxcosx

Consider left side

cos20°cos40°cos80°

= $\frac{1}{2sin20}$ (2sin20°cos20°)cos40°cos80°

= $\frac{1}{4sin20}$ (2sin40°cos40°)cos80°

= $\frac{1}{4sin20}$ (sin80°cos80° )

= $\frac{1}{8sin20}$ (2sin80°cos80° )

= $\frac{1}{8sin20}$ . sin160°

= $\frac{1}{8sin20}$ . sin(180 - 20)°

= $\frac{1}{8sin20}$ . sin20°

= $\frac{1}{8}$ = right side , thus proven

viva [34]2 years ago

7 0

Step-by-step explanation:

hope its helps you have a great day keep smiling be happy stay safe ☺

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How do you writ 1.660 in scientific notation

belka [17]

Answer:

$1.66 * 10^{0}$

Step-by-step explanation:

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3 years ago

80,000/100 in its lowest term

Viktor [21]

Answer is 800. Mark as branliest tq

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3 years ago

Read 2 more answers

Check my answer? Please, no joking around guys.

WITCHER [35]

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3 years ago

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What is the scale factor for pre-image IJKH to image MNOL?

solniwko [45]

Answer:

Step-by-step explanation:

Given are two rectangles MNOL and IJKH

MNOL is the image and IJKH is the preimage.

OBviously similarity is preserved between these.

Hence sides will be proportional

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This can also be written as

Scale factor square = $k^2=\sqrt{ \frac{areaI}{area2} }$

Scale factor = square root of ratio of rectangle areas

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4 years ago

Sushil is 6 years older than Brian. Caroline is 5 years younger than Brian. If the total of their ages is 64, how old is the you

Nadusha1986 [10]

Answer:

16 years old

Step-by-step explanation:

Let's use the letters s, b, and c for Sushil, Brian, and Caroline's ages. Sushil is the oldest, followed by Brian, and then Caroline, the youngest. From the problem description, we can set up three equations:

s = b + 6 (Sushil is 6 years older than Brian)

c = b - 5 (Caroline is 5 years younger than Brian)

s + b + c = 64 (The total of their ages is 64)

Since s and c are already in terms of b, we can substitute them into the last equation and solve to find Brian's age:

(b + 6) + b + (b - 5) = 64

3b + 1 = 64

3b = 63

b = 21

Now that we know Brian's age, we can simply subtract 5 to find Caroline's:

c = b - 5 = 21 - 5 = 16 years old.

8 0

3 years ago

Prove that:cos20°cos40°cos80°=1/8​

Prove that:cos20°cos40°cos80°=1/8