Section 6.7

By cssp

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1. (a) f'(x) = 3\cosh(3x)

(c) f'(t) = 6t\sinh(t)\sinh(2t) + 3t\cosh(t)\cosh(2t) + 3\sinh(t)\cosh(t)

(e) y'(t) = 40t^2\cosh(4t)\sinh(4t) + 10t\cosh^2(4t)

2. (a) \displaystyle{\int \sinh(3x)dx = \frac{1}{3}\cosh(3x) + c}

(c) \displaystyle{\int \sinh(z)\cosh(z)dz = \frac{1}{2}\sinh^2(z) + c}

(e) \displaystyle{\int e^{-2t}\cosh(2t)dt = \frac{1}{2}t - \frac{1}{8}e^{-4t} + c}

(g) \displaystyle{\int 5t^2\cosh(2t)dt = \frac{5}{2}t^2\sinh(2t) - \frac{5}{2}t\cosh(2t) + \frac{5}{4}\sinh(2t) + c}

4. (a) \displaystyle{\int \frac{1}{\sqrt{4+x^2}} \ dx = \sinh^{-1}\left(\frac{x}{2}\right) + c}

(c) \displaystyle{\int \frac{3}{\sqrt{9+3t^2}} \ dt = \sqrt{3}\sinh^{-1}\left(\frac{t}{\sqrt{3}}\right) + c}

(d) For x < -1 , \displaystyle{\int \frac{1}{\sqrt{x^2-1}} \ dx = -\cosh^{-1}|x| + c}.

6. (a) \displaystyle{f'(x) = 12x\mathrm{sech}^2(4x) + 3\tanh(4x)}

(c) \displaystyle{h'(\theta) = 8\tanh(\theta)\mathrm{sech}^3(\theta) - 4\tanh^3(\theta)\mathrm{sech}(\theta)}

7. (a) \displaystyle{\int \tanh(x)dx = \log(\cosh(x)) + c}

(c) \displaystyle{\int \frac{1}{4 - x^2} \ dx = \frac{1}{2}\tanh^{-1}\left(\frac{x}{2}\right) + c}

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