Which technique is best to use for x² + 4x = 15
1 answer:
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Answer:
5. 88.0°
6. 13.0°
7. 52.4°
8. 117.8°
Step-by-step explanation:
For angle A between sides b and c, the law of cosines formula can be solved to find the angle as ...
A = arccos((b² +c² -a²)/(2bc))
When calculations are repetitive, I find a spreadsheet useful. It doesn't mind doing the same thing over and over, and it usually makes fewer mistakes.
Here, the side opposite x° is put in column 'a', so angle A is the value of x. The order of the other two sides is irrelevant.
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<em>Additional comment</em>
The spreadsheet ACOS function returns the angle in radians. The DEGREES function must be used to convert it to degrees. The formula for the first problem is shown here:
=degrees(ACOS((C3^2+D3^2-B3^2)/(2*C3*D3)))
As you can probably tell from the formula, side 'a' is listed in column B of the spreadsheet.
The spreadsheet rounds the results. This means the angle total is sometimes 179.9 and sometimes 180.1 when we expect the sum of angles to be 180.0.
