Given cos a= 3/5, sin b = 5/13 and a and b are first quadrant angles find cos(a + b) a. 1/3 b. 16/65 c. -33/65 explain

Option B is correct.

Value of cos(a+B) is,  

Step-by-step explanation:

Using the formula:

Given the values:

and

Using trigonometric identity:

or

or

Find the value of sin a and cos B;

Using trigonometric identity:

=

Similarly;

=

Substitute these given values equation [1] we have;

then;

Since, the angles a and B are in first quadrant angles therefore the value of cos(a+B) is,

b

step-by-step explanation: