Answer:
about 0.108253
Explanation:
You want the product sin(20°)·sin(30°)·sin(40°)·sin(80°).
Sine
The values of the sine function are found using a table or calculator. The attachment shows the list of sine values and their product.
The product is about 0.108253.
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Additional comment
We're not sure what to make of the expression sin 20° . sin 30° .... Elsewhere on the page, a proper multiplication symbol (×) is used. A decimal point makes no sense in the context of this expression. We know that a baseline dot is sometimes intended to signify multiplication, so that is the interpretation used above.
If this is intended to be asking for four (4) sine values, they are shown in the attachment.