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If cos theta = -5/13 where 180° < theta < 360°, determine, without using a calculator, the value of: 1.1 sin² theta 1.2 tan(360° - theta) 1.3 cos(theta - 135°)
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3 partsStep-by-step solution
7 steps1. Given where .
Since is negative and , lies in Quadrant III.
Step 1: Determine .
Using the identity :
Since is in Quadrant III, is negative.
Step 2: Determine .
Part 1.1
Calculate .
From Step 1:
The value of is .
Part 1.2
Calculate .
Using the reduction formula :
The value of is .
Part 1.3
Calculate .
Using the compound angle formula :
We know .
And .
Substitute the values of , , , and :
The value of is .
2. Simplify the expression to a single trigonometric term.
Simplify the numerator.
Using reduction formulas: and .
This is the double angle identity for sine: .
Simplify the denominator.
Using the cofunction identity: .
This is the double angle identity for cosine: .
Combine the simplified numerator and denominator.
The simplified expression is .
3. Calculate the value of the expression .
Determine the number of terms and simplify each term.
The angles are . This is an arithmetic progression with a common difference of .
The number of terms is found by , which gives , so , and .
Each term can be written using the reduction formula :
...
Rewrite the product.
The product is .
Since there are 44 terms (an even number), the product of the negative signs is positive.Pair the terms using the identity .
We can pair terms such that their product is 1: .
The terms in the product are .
We form pairs:
...
The last pair will be .
There are such pairs.Calculate the final product.
Since each pair multiplies to 1, the entire product is .
The value of the expression is .
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