6 uždavinys

Sprendimas:

$cos(A)^{2}-1$ = $(1-sin(A)^{2})-1$ = $(1-(\frac{1}{4})^{2})-1$ = $(1-\frac{1}{16})-1$ = $1-\frac{1}{16}-1$ = $-\frac{1}{16}$

Atsakymas: C $-\frac{1}{16}$