1. Solving for t

5 = 11-10cos(0.1pit)

-6 = -10cos(0.1pit)

-6/-10 = cos(0.1pit)

3/5 = cos(0.1pit)

cos^-1(3/5) / (0.1pi) = t

t = 169.118 however the answer should be 2.952

2. Your method is fine, but as you're working in terms of pi, it's radians that you should be using.

3. Looks like your calculator is in degrees mode instead of radians mode - nothing wrong with the working

4. Originally Posted by Devi09
5 = 11-10cos(0.1pit)

-6 = -10cos(0.1pit)

-6/-10 = cos(0.1pit)

3/5 = cos(0.1pit)

cos^-1(3/5) / (0.1pi) = t

t = 169.118 however the answer should be 2.952
The answers are the same but in different "units"

the first one is in degree's and the 2nd one is in radians.

Just change your calculator to Radian mode and you will get the same thing.

Too slow X2