Question

Given: tangent A = negative StartRoot 15 EndRoot What is the value of Tangent (A minus StartFraction pi over 4 EndFraction)?

Answer 1

Probably D ( -√15-1/1-√15)

Explanation:

it was in adidemiokin's answer before they rationalized it. Couldn't find the darn answer anywhere else. I'm on my 3rd attempt on the EDGE precalc Unit test hopefully D is right.

Answer 2

( √15 + 8)/7

Explanation:

TanA = -√15

.we are to find tan(A-π/4).

In trigonometry

Tan(A-B) = TanA - TanB/1+ tanAtanB

Hence:

tan(A-π/4) = TanA - Tanπ/4/1+ tanAtanπ/4

Substitute tan A value into the formula

tan(A-π/4) = -√15-tanπ/4 / 1+(-√15)(tanπ/4

tan(A-π/4) = -√15-1/1-√15

Rationalize

-√15-1/1-√15 × 1+√15/1+√15

= -√15-√225-1-√15/(1-√225)

= -2√15-15-1/1-15

= -2√15 -16/(-14)

= -2(√15+8)/-14

= √15 + 8/7

Hence the required value is ( √15 + 8)/7