Question

if sec A is equal to 17/8,prove that 1-2 sin square A is equal to cos square -1

Answer 1

secA=17/8, cosA=8/17
LHS= 1-2sin^2A
= 1-2+2cos^2A
= -1 + 2.64/289
= -289+128/289
= -161/289

RHS= 2cos^2A-1
= 2.64/289-1
= 128-289/289
= -161/289