Four Integrals Triangle
1. Problem (a): Evaluate $\int (1 - \frac{1}{w})\cos(w - \ln(w))\, dw$.
Step 1: Let $u = w - \ln(w)$. Then, compute $du$.
$$du = \frac{d}{dw}(w) - \frac{d}{dw}(\ln w) = 1 - \frac{1}{w}$$
Step 2: Substitute in the integral:
$$\int (1 - \frac{1}{w}) \cos(w - \ln w) dw = \int \cos(u) du$$
Step 3: Integrate:
$$\int \cos(u) du = \sin(u) + C = \sin(w - \ln w) + C$$
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2. Problem (b): Evaluate $\int 3(8y - 1) e^{4y^2 - y} dy$.
Step 1: Let $v = 4y^2 - y$, then compute $dv$.
$$dv = 8y - 1 dy$$
Step 2: Rewrite the integral:
$$\int 3(8y - 1) e^{4y^2 - y} dy = 3 \int (8y - 1) e^v dy$$
Since $dv = (8y - 1) dy$, then $(8y - 1) dy = dv$, so
$$= 3 \int e^v dv = 3 e^v + C = 3 e^{4y^2 - y} + C$$
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3. Problem (c): Evaluate $\int x^2 (3 - 10x^3)^4 dx$.
Step 1: Let $t = 3 - 10x^3$.
Compute $dt$:
$$dt = -30 x^2 dx \implies x^2 dx = -\frac{dt}{30}$$
Step 2: Substitute in the integral:
$$\int x^2 (3 - 10x^3)^4 dx = \int t^4 \left(-\frac{dt}{30}\right) = -\frac{1}{30} \int t^4 dt$$
Step 3: Integrate:
$$-\frac{1}{30} \cdot \frac{t^5}{5} + C = -\frac{t^5}{150} + C = -\frac{(3 - 10x^3)^5}{150} + C$$
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4. Problem (d): Evaluate $\int \frac{x}{\sqrt{1 - 4x^2}} dx$.
Step 1: Let $w = 1 - 4x^2$.
Compute $dw$:
$$dw = -8x dx \implies x dx = -\frac{dw}{8}$$
Step 2: Substitute in the integral:
$$\int \frac{x}{\sqrt{1 - 4x^2}} dx = \int \frac{x}{\sqrt{w}} dx$$
Express $x dx$:
$$x dx = -\frac{dw}{8}$$
So the integral becomes:
$$\int \frac{x}{\sqrt{w}} dx = \int \frac{-\frac{dw}{8}}{\sqrt{w}} = -\frac{1}{8} \int w^{-1/2} dw$$
Step 3: Integrate:
$$-\frac{1}{8} \cdot 2 w^{1/2} + C = -\frac{1}{4} \sqrt{w} + C = -\frac{1}{4} \sqrt{1 - 4x^2} + C$$
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5. Geometry problem: Triangle with vertices A(0,0), B(4,0), and C(4,6).
To find hypotenuse length (side AC):
$$\text{length} = \sqrt{(4-0)^2 + (6-0)^2} = \sqrt{16 + 36} = \sqrt{52}$$
Simplify:
$$\sqrt{52} = 2\sqrt{13}$$
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Final answers:
(a) $\sin(w - \ln w) + C$
(b) $3 e^{4y^{2} - y} + C$
(c) $-\frac{(3 - 10x^{3})^5}{150} + C$
(d) $-\frac{1}{4} \sqrt{1 - 4x^{2}} + C$
Triangle hypotenuse length: $2\sqrt{13}$