- #1

salman213

- 302

- 1

**1.x = rcos(a)cos(a)**

x is known

r is known

I can't seem to get this!

x = -2

r = 7

therefore

-2/7 = cos(a)*cos(a)

so..

-2/7 = cos^2(a)

i know cos^2(a) = 1 + cos2a / 2

-2/7 = 1 + cos2a / 2

so

-4/7 -1 = cos2a

I cannot take cos inverse of this value since it is "greater" than 1 (-1.57)

the book says the angle is 106.6 degrees!

HELP!

x is known

r is known

I can't seem to get this!

x = -2

r = 7

therefore

-2/7 = cos(a)*cos(a)

so..

-2/7 = cos^2(a)

i know cos^2(a) = 1 + cos2a / 2

-2/7 = 1 + cos2a / 2

so

-4/7 -1 = cos2a

I cannot take cos inverse of this value since it is "greater" than 1 (-1.57)

the book says the angle is 106.6 degrees!

HELP!