Bantu no 2 ya makasihh trigonometri ni

sin A = 3/5
cos A = √(1 - sin² A) = 4/5

tan B = 1/7
sin B = 1/√(7² + 1²) = 1/√50
cos B = 7/√50

cos (A + B)
= cos A cos B - sin A sin B
= 4/5 . 7/√50 - 3/5 . 1/√50
= 25/(5 . 5√2)
= 25/(25√2)
= 1/√2
= 1/2 √2