Step-by-step explanation:
(i)
Using cos(a - b) = cos a cos b + sin a sin b
[tex]\frac{4}{5}[/tex] = cos a cos b + [tex]\frac{1}{5}[/tex]
cos a cos b = [tex]\frac{4}{5} -\frac{1}{5} = \frac{3}{5}[/tex]
(ii)
Using cos(a + b) = cos a cos b - sin a sin b
cos(a + b) = [tex]\frac{3}{5}-\frac{1}{5}=\frac{2}{5}[/tex]
(iii)
Using cot a = [tex]\frac{cos a}{sin a}[/tex]
[tex]=(\frac{cos A}{sin A} )(\frac{cos B}{sin B} )[/tex]
[tex]=\frac{cos A cos B}{sin A sin B}[/tex]
[tex]=\frac{\frac{3}{5} }{\frac{1}{5} }[/tex] [tex]=\frac{3}{5}[/tex] × [tex]5[/tex]
= 3
please give me a brainliest answer
