In this worksheet, we will practice using the product-to-sum identity to evaluate a trigonometric expression.

**Q3: **

Simplify .

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**Q4: **

Write the expression as a sum or difference of trigonometric expressions.

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**Q5: **

Find the exact value of .

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**Q6: **

Write the expression as a product of trigonometric expressions.

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**Q7: **

Find the value of , given where .

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**Q8: **

Find the value of given .

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**Q9: **

Find given and where and are acute angles.

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**Q10: **

is a triangle where and . Find without using a calculator.

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**Q11: **

Find, without using a calculator, the value of given where and where .

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**Q12: **

Find, without using a calculator, the value of given where and where .

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**Q13: **

Find the value of given where is the smallest positive angle and where .

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**Q14: **

The intensity of an electric current is given by where is the time in seconds. Find the intensity after one second without using a calculator using sum and product formulae.

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**Q15: **

Find the value of .

**Q16: **

Find the value of .