jika tan α=3/4 dan tan β =7/24 dengan α dan β lancip maka cos(α+β) =

Tan a = 3/4. R²= √3²+4²
Cos a = 4/5 √9+16
Sin a= 3/5 R²=√25
R = 5

Tan b= 7/24. R²= √7²+24²
Cos b= 24/25 = √49+576
Tan b=7/25 = √625
R= 25

Cos (a+b) = cos a.cos b - sin a.sinb
= 4/5.24/25 - 3/5.7/25
= 96/125 - 21/125
= 75/125
= 3/5