Find the Exact Value sin(70 degrees )

Problem

sin(70)

Solution

1. Identify the expression as the sine of an angle in degrees.

2. Determine if the angle is a standard reference angle (such as 0 30 45 60 or 90.

3. Recognize that 70 is not a standard reference angle and cannot be expressed as a simple sum or difference of standard angles to yield a basic radical form.

4. Conclude that the exact value is represented by the expression itself, or it can be written in terms of its cofunction.

5. Apply the cofunction identity sin(θ)=cos(90−θ)

sin(70)=cos(90−70)

sin(70)=cos(20)

Final Answer

sin(70)=sin(70)

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