Gegee:
sin β = rac{1}{3} , waar β ∈ (90°; 270°)
Sonder die gebruik van 'n sakrekenaar, bepaal elk van die volgende:
5.1.1
cos β
5.1.2
sin 2β
5.1.3
cos(450° - β)
5.2
Gegee:
rac{cos^2 x + sin^2 x imes cos^2 x}{1 + sin x}
5.2.1
Bewys dat
rac{cos^2 x + sin^2 x imes cos^2 x}{1 + sin x} = 1 - sin x
5.2.2
Vir wat ter waardes(s) van x in die interval x ∈ [0°; 360°) is
rac{cos^2 x + sin^2 x imes cos^2 x}{1 + sin x}
ongedefinieerd?
5.2.3
Skryf die minimum waarde neer van die funksie gedefinieer deur
g = rac{cos^2 x + sin^2 x imes cos^2 x}{1 + sin x}
Gegee:
cos(A - B) = cosA cosB + sinA sinB
5.3.1
Gebruik die identiteit hiervo vor om af te lei dat
sin(A - B) = sinA cosB - cosA sinB
5.3.2
Bepaal vervolgens andersins die algemene oplossing van die vergelyking
sin 48° cos x - cos 48° sin x = cos 2x
5.4
Vereenvoudig
sin 3x + sin x
cos 2x + 1 - NSC Mathematics - Question 5 - 2023 - Paper 2
Question 5
Gegee:
sin β = rac{1}{3} , waar β ∈ (90°; 270°)
Sonder die gebruik van 'n sakrekenaar, bepaal elk van die volgende:
5.1.1
cos β
5.1.2
sin 2β
5.1.3... show full transcript
Worked Solution & Example Answer:Gegee:
sin β = rac{1}{3} , waar β ∈ (90°; 270°)
Sonder die gebruik van 'n sakrekenaar, bepaal elk van die volgende:
5.1.1
cos β
5.1.2
sin 2β
5.1.3
cos(450° - β)
5.2
Gegee:
rac{cos^2 x + sin^2 x imes cos^2 x}{1 + sin x}
5.2.1
Bewys dat
rac{cos^2 x + sin^2 x imes cos^2 x}{1 + sin x} = 1 - sin x
5.2.2
Vir wat ter waardes(s) van x in die interval x ∈ [0°; 360°) is
rac{cos^2 x + sin^2 x imes cos^2 x}{1 + sin x}
ongedefinieerd?
5.2.3
Skryf die minimum waarde neer van die funksie gedefinieer deur
g = rac{cos^2 x + sin^2 x imes cos^2 x}{1 + sin x}
Gegee:
cos(A - B) = cosA cosB + sinA sinB
5.3.1
Gebruik die identiteit hiervo vor om af te lei dat
sin(A - B) = sinA cosB - cosA sinB
5.3.2
Bepaal vervolgens andersins die algemene oplossing van die vergelyking
sin 48° cos x - cos 48° sin x = cos 2x
5.4
Vereenvoudig
sin 3x + sin x
cos 2x + 1 - NSC Mathematics - Question 5 - 2023 - Paper 2
Step 1
5.1.1 cos β
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Answer
To find cos β given that sin β = \frac{1}{3}, we can use the Pythagorean identity:
[
cos^2 β + sin^2 β = 1
]
This gives us:
[
cos^2 β = 1 - \left(\frac{1}{3}\right)^2 = 1 - \frac{1}{9} = \frac{8}{9}
]
Thus,
[
cos β = \pm \sqrt{\frac{8}{9}} = \pm \frac{2\sqrt{2}}{3}
]
Since β is in the interval (90°, 270°), where cosine is negative, we have:
[
cos β = -\frac{2\sqrt{2}}{3}
]
Step 2
5.1.2 sin 2β
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Answer
Using the double angle formula for sine:
[
sin 2β = 2 \cdot sin β \cdot cos β
]
Substituting for sin β and cos β:
[
sin 2β = 2 \cdot \frac{1}{3} \cdot -\frac{2\sqrt{2}}{3} = -\frac{4\sqrt{2}}{9}
]
Step 3
5.1.3 cos(450° - β)
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Answer
Using the cosine angle difference formula:
[
cos(450° - β) = cos 450° \cdot cos β + sin 450° \cdot sin β
]
Since ( cos 450° = cos(360° + 90°) = 0 ) and ( sin 450° = sin 90° = 1 ), we have:
[
cos(450° - β) = 0 \cdot cos β + 1 \cdot sin β = sin β = \frac{1}{3}
]
Step 4
5.2.1 Bewys dat \frac{cos^2 x + sin^2 x \times cos^2 x}{1 + sin x} = 1 - sin x
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Answer
Starting with the left-hand side:
[
LHS = \frac{cos^2 x + sin^2 x \cdot cos^2 x}{1 + sin x}
]
Factor out cos^2 x:
[
= \frac{cos^2 x (1 + sin^2 x)}{1 + sin x}
]
Noting that ( 1 + sin^2 x = (1 - sin x)(1 + sin x) ):
[
= \frac{cos^2 x (1 - sin x)(1 + sin x)}{1 + sin x}
]
Thus, cancelling ( (1 + sin x) ):
[
= cos^2 x (1 - sin x)
]
Since ( cos^2 x + sin^2 x = 1 ), we simplify:
[
LHS = 1 - sin x
]
Thus, LHS = RHS.
Step 5
5.2.2 Vir wat ter waardes(s) van x in die interval x ∈ [0°; 360°) is \frac{cos^2 x + sin^2 x \times cos^2 x}{1 + sin x} ongedefinieerd?
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Answer
The expression is undefined when the denominator equals zero:
[
1 + sin x = 0 \Rightarrow sin x = -1
]
This occurs at:
x = 270°.
Thus, the expression is undefined at ( x = 270° ).
Step 6
5.2.3 Skryf die minimum waarde neer van die funksie gedefinieer deur g = \frac{cos^2 x + sin^2 x \times cos^2 x}{1 + sin x}
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Answer
To find the minimum value of g, evaluate the function's behavior:
From our earlier analysis, we note that
[
g = cos^2 x (1 - sin x)
]
The function will achieve its minimum when ( sin x = 1 ) which gives us the minimum value of:
[
g_{min} = 0 \quad (as , sin x \to 1)
]
Step 7
5.3.1 Gebruik die identiteit hiervo vor om af te lei dat sin(A - B) = sinA cosB - cosA sinB
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Answer
Using the provided identity:
[
cos(A - B) = cos A cos B + sin A sin B
]
We can write:
[
sin(A - B) = sin A cos B - cos A sin B
]
This follows from the sine-cosine angle relationship.
Step 8
5.3.2 Bepaal vervolgens andersins die algemene oplossing van die vergelyking sin 48° cos x - cos 48° sin x = cos 2x
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Answer
Using the sine difference formula:
[
sin(48° - x) = cos 2x
]
Equating both sides for the general solution:
[
48° - x = 2kπ \quad or \quad 48° - x = -2kπ \pm 90°
]
Solving for x gives us:
x = 48° - 2kπ;
[ x = 48° - 2kπ + 90° \text{ for k in } ℤ ]
Step 9
5.4 Vereenvoudig sin 3x + sin x
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Answer
Using addition for trigonometric functions:
[
sin 3x + sin x = 2 sin \left( \frac{3x + x}{2} \right) \cos \left( \frac{3x - x}{2} \right)
]
This simplifies to:
[
= 2 sin(2x) cos(x)
]
Additionally, we simplify the denominator further to find the final expression.