Thread: trionometrey

Can someone please check my triq questions thanks!
Thanks!

Hello, bay!

1) The exact value of: 6·cos(-61π/6) - 2·sin(13π/4) is:
. . . . . . _ . . ._ . . . . . . . . ._ . . . . . . . . _ . . . . . . _ . . _
. . A. 3√3 + √2 . . B. -3 + √2 . . C. -3 - √2 . . D. 3√3 - √2

Since -61π/6 = -π/6 .and .13π/4 = 5π/4

we have: .6·cos(-π/6) - 2·sin(5π/4)
. . . . . . . . . _ . - . . - . _ . - . . - . . ._ . . ._
. . . . = . 6(√3/2) - 2(-√2/2) . = . 3√3 + √2 . answer A


I agree with your answers to #2, 3, and 4.

5. Another form of .cos(30° - A) + sin(60° + A) is:
. . . . . . . . . . . . . _ . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . _
. . A. sin A . . B. √3·cos A + sin A . . C. (√3/2)·sin A + cos A . . D. √2·sin A + cos A

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ._
cos(30° - A) .= .cos 30°·cos A + sin 30°·sin A .= .(√3/2)·cos A + (1/2)·sin A
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ._
sin(60° + A) .= .sin 60°·cos A + cos 60°·sin A .= .(√3/2)·cos A + (1/2)·sin A

. . . . . . . . . . . . . . . . . . . . . . . . . . . ._
Add: .cos(30° - A) + sin(60° + A) .= .√3·cosA + sin A . answer B