Prove that sin20sin40sin60sin80=3/16
1 answer:
We'll use the following properties of sine and cosine to prove this:
Then it's just a matter of filling it in...
sin20sin40 * sin60sin80 = 1/2(cos20 - cos60) * 1/2 (cos20 - cos140) =
1/8( cos40 + 1 - cos160 - cos120 - cos40 - cos80 + cos80 + cos200) =
1/8(1 - cos160 - cos120 + cos200) =
1/8(1 - cos160 - cos120 + cos160) =
1/8(1 - cos120 ) = 1/8( 1 + 1/2 ) = 3/16
Then it's just a matter of filling it in...
sin20sin40 * sin60sin80 = 1/2(cos20 - cos60) * 1/2 (cos20 - cos140) =
1/8( cos40 + 1 - cos160 - cos120 - cos40 - cos80 + cos80 + cos200) =
1/8(1 - cos160 - cos120 + cos200) =
1/8(1 - cos160 - cos120 + cos160) =
1/8(1 - cos120 ) = 1/8( 1 + 1/2 ) = 3/16
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Answer:
The Amount of tax paid on the cell phone is $11.9
Step-by-step explanation:
Given as :
The cost of the cell phone = x = $170
The tax rate of the cell phone = r = 7% of the phone cost
Let The Amount of tax paid on the cell phone = $y
<u>Now, According to question</u>
The Amount of tax paid on the cell phone = 7 % of cost of the cell phone
i.e y = 7% of x
Or, y = × x
Or, y = × $170
Or, y =
∴ y = 7 × 1.7
i.e y = $11.9
So,The Amount of tax paid on the cell phone = y = $11.9
Hence, The Amount of tax paid on the cell phone is $11.9 Answer
To solve this problem, we must imagine the triangles and parallel lines which are formed. It is best to draw the triangle described in the problem so that you can clearly understand what I will be talking about.
The first step we have to do is to make an equality equation in triangle ABC.
In triangle ABC, we are given that lines XY and BC are two parallel lines (XY || BC). Therefore this means that:
AX / XB = AY / YC ---> 1
The next step is to make an equality equation in triangle AXC.
We are given that lines ZY and XC are two parallel lines (ZY || XC). Therefore this also means that:
AZ / ZX = AY / YC ---> 2
Combining 1 and 2 since they have both AY / YC in common:
AX / XB = AZ / ZX
we are given that:
AZ = 8, ZX = 4 therefore AX = AZ + ZX = 12, hence
12 / XB = 8 / 4
XB = 6
