5.1 Simplify (WITHOUT THE USE OF A CALCULATOR)
sin(180° - 360°) - NSC Mathematics - Question 5 - 2016 - Paper 2

Question 5

5.1 Simplify (WITHOUT THE USE OF A CALCULATOR)
sin(180° - 360°) . cos(x) . tan(180° + x) . cos(-x)
tan(-x) . cos(90° - x) . sin(90° - x)
5.2 Prove the identity:
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Worked Solution & Example Answer:5.1 Simplify (WITHOUT THE USE OF A CALCULATOR)
sin(180° - 360°) - NSC Mathematics - Question 5 - 2016 - Paper 2
5.1 Simplify (WITHOUT THE USE OF A CALCULATOR)

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To simplify the expression:
Start with:
extExpression=extsin(180°−360°)imesextcos(x)imesexttan(180°+x)imesextcos(−x) exttan(−x)imesextcos(90°−x)imesextsin(90°−x)
Using trigonometric identities:
- \ ext{sin}(180° - θ) = ext{sin} θ
- \ ext{cos}(180° + θ) = - ext{cos} θ
- \ ext{cos}(-θ) = ext{cos} θ
- \ ext{tan}(-θ) = - ext{tan} θ
- \ ext{cos}(90° - θ) = ext{sin} θ
Apply these identities to the expression:
=extsin(360°)imesextcos(x)imes(−exttan(x))imesextcos(x)imes(−exttan(x))imesextsin(x)imesextsin(x)
With sin(360°) = 0, the entire expression simplifies to:
extExpression=−extcos(x)
5.2 Prove the identity:

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To prove the identity:
Start with the left-hand side (LHS):
LHS=1+cosxsinx+sinx1+cosx
Finding a common denominator:
LHS=sinx(1+cosx)sin2x+(1+cosx)(1+cosx) =sinx(1+cosx)sin2x+1+2cosx+cos2x
Now using the Pythagorean identity, (\sin^2 x + \cos^2 x = 1):
=sinx(1+cosx)2+2cosx=sinx2
Thus, (LHS = RHS), confirming the identity.
5.3 Use compound angles to show that:

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To show that:
cos2x=2cos2x−1
Using the compound angle formula for cosine:
We can express (\sin^2 x) in terms of (\cos^2 x):
sin2x=1−cos2x
Substituting this into the equation:
cos2x=cos2x−(1−cos2x)=2cos2x−1
This confirms the identity.
5.4 Determine the general solution for x if:

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To solve:
Rearranging gives:
The general solutions for (\cos \theta = -1) are:
Thus:
5.5 In \( \triangle ABC: \; A + B = 90° \). Determine the value of \( \sin A \cdot \cos B + \cos A \cdot \sin B \).

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Using the identity for sine of a sum:
Since (A + B = 90°), this implies:
Thus:
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