Math 121 Assignment 2 Due Friday January 22 1. Find the function f that satisfies the equation Z 1 f (t) dt. 2f (x) + 1 = 3 x 2. Find the area of (a) the plane region bounded between the two curves y = x42 and y = 5 − x2 . (b) Find the area of the closed loop of the curve y 2 = x4 (2 + x) that lies to the left of the origin. 3. Evaluate the integrals Z 4√ (a) 9t2 + t4 dt. Z0 t t 2 2 (b) cos sin dt. 5 2 Z (c) cos4 x dx. Z dx (d) . x e +1 Z 2 x dx . (e) 4 0 x + 16 Z πp 2 (f ) 1 − sin(θ) dθ. 0 4. Use mathematical induction to show that for every positive integer k, n X nk+1 nk k j = + + Pk−1 (n), k+1 2 j=1 where Pk−1 is a polynomial of degree at most k − 1. Deduce from this that Z a ak+1 xk dx = . k+1 0 5. Does the function Z 2x−x2 1 F (x) = dt cos 1 + t2 0 have a maximum or minimum value? Justify your answer. 1 2 6. (a) If m, n are integers, compute the integrals Z π Z π Z π sin mx cos nx dx. sin mx sin nx dx, cos mx cos nx dx, −π −π −π (b) Suppose that for some positive integer k, k a0 X f (x) = + (an cos nx + bn sin nx) 2 n=1 holds for all x ∈ [−π, π]. Find integral formulas for the coefficients a0 , an , bn with the integrand involving f of course. (Remark: The coefficients a0 , an , bn are called the Fourier coefficients of f . Fourier coefficients arise in a variety of contexts, such as communications and signal processing. If f is a musical note, then the integers n for which an or bn are nonzero are precisely the frequencies comprising the note.)