Answer:
This is how tackle this type of problem:
Draw a right triangle with the indicated sides: side opposite the angle = 12 and hypotenuse = 13
Then, calculate the 3rd side by Pythagoras: x2 + 122 = 132
x2 = 169 - 144
x2 = 25
x = 5
Now, we have all 3 sides of our diagram triangle, so we can find all the trig ratios for the angle.
Next, we use the double angle formula to simplify cos(x + 30) = cos x cos 30 - sin x sin 30
= 5/13 . √3/2 - 12/13 . 1/2
= 5√3 /26 - 6/13
= (5√3 - 12) / 26
Step-by-step explanation:
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