# Using Chebyshev Polynomial #T_n (x)=cosh( n( arc cosh(x))), x > = 1# and the recurrence relation #T_(n+2)(x)=2xT_(n+1)(x) - T_n (x)#, with #T_0(x)=1 and T_1(x)=x#, how do you porve that #cosh(7 arc cosh(1.5))=421.5?#

##### 1 Answer

Oct 4, 2016

using

From wiki Chebyshev Polynomials Table,.

#T_7(x)=64x^7-112x^5+56x^3-7x