Solved on Feb 18, 2024

Find the derivative of y=cos1(sin(x))y = \cos^{-1}(\sin(x)).

STEP 1

Assumptions
1. The function y=cos1(sin(x))y=\cos^{-1}(\sin(x)) is defined for values of xx where sin(x)\sin(x) falls within the range of the cos1\cos^{-1} function, which is [1,1][-1,1].
2. The range of the cos1\cos^{-1} function is [0,π][0, \pi].
3. The domain of the sin\sin function is all real numbers.

STEP 2

Understand the relationship between the sine and cosine functions. The sine function can be expressed in terms of cosine by using the complementary angle identity:
sin(x)=cos(π2x)\sin(x) = \cos\left(\frac{\pi}{2} - x\right)

STEP 3

Replace sin(x)\sin(x) with cos(π2x)\cos\left(\frac{\pi}{2} - x\right) in the original equation:
y=cos1(cos(π2x))y = \cos^{-1}\left(\cos\left(\frac{\pi}{2} - x\right)\right)

STEP 4

Recognize that cos1(cos(θ))=θ\cos^{-1}(\cos(\theta)) = \theta for θ\theta in the range [0,π][0, \pi]. Therefore, if π2x\frac{\pi}{2} - x is within this range, we can simplify the equation to:
y=π2xy = \frac{\pi}{2} - x

STEP 5

Determine the range of xx for which π2x\frac{\pi}{2} - x falls within the range [0,π][0, \pi]. This occurs when:
0π2xπ0 \leq \frac{\pi}{2} - x \leq \pi

STEP 6

Solve the inequality for xx to find the domain where the simplification is valid:
π2x3π2-\frac{\pi}{2} \leq x \leq \frac{3\pi}{2}

STEP 7

Now we need to consider the values of xx outside the range [π2,3π2][-\frac{\pi}{2}, \frac{3\pi}{2}]. For these values, cos1(sin(x))\cos^{-1}(\sin(x)) does not directly simplify to π2x\frac{\pi}{2} - x because sin(x)\sin(x) might not be equal to cos(π2x)\cos(\frac{\pi}{2} - x) due to periodicity and the range of the cos1\cos^{-1} function.

STEP 8

For xx outside the range [π2,3π2][-\frac{\pi}{2}, \frac{3\pi}{2}], we need to find an equivalent angle θ\theta such that sin(x)=sin(θ)\sin(x) = \sin(\theta) and θ\theta is within the range [0,π][0, \pi] since that is the range of the cos1\cos^{-1} function.

STEP 9

Use the fact that sin(x)\sin(x) has a period of 2π2\pi to find an equivalent angle θ\theta within the desired range. We can express θ\theta as:
θ=x2πk\theta = x - 2\pi k
where kk is an integer chosen such that θ\theta is in the range [0,π][0, \pi].

STEP 10

For xx outside the range [π2,3π2][-\frac{\pi}{2}, \frac{3\pi}{2}], we use the angle θ\theta to rewrite the original equation as:
y=cos1(sin(θ))y = \cos^{-1}(\sin(\theta))

STEP 11

Since θ\theta is now within the range [0,π][0, \pi], we can again use the complementary angle identity:
y=cos1(cos(π2θ))y = \cos^{-1}(\cos(\frac{\pi}{2} - \theta))

STEP 12

Simplify the equation using the fact that cos1(cos(θ))=θ\cos^{-1}(\cos(\theta)) = \theta for θ\theta in the range [0,π][0, \pi]:
y=π2θy = \frac{\pi}{2} - \theta

STEP 13

Replace θ\theta with x2πkx - 2\pi k to find the general solution for yy:
y=π2(x2πk)y = \frac{\pi}{2} - (x - 2\pi k)

STEP 14

Simplify the expression for yy:
y=π2x+2πky = \frac{\pi}{2} - x + 2\pi k

STEP 15

The final solution for yy depends on the value of xx. If xx is in the range [π2,3π2][-\frac{\pi}{2}, \frac{3\pi}{2}], then y=π2xy = \frac{\pi}{2} - x. If xx is outside this range, then yy can be expressed as y=π2x+2πky = \frac{\pi}{2} - x + 2\pi k, where kk is an integer chosen such that the resulting angle is in the range [0,π][0, \pi].

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