jika tan = 0,75 (di kuadran 1) mka tentukan cos 2

tan A = 0, 75 = 75/100 = 3/4 
maka depan = 3
samping = 4
maka miring = akar {4^2 - 3^2
= akar {16 -9}
= akar 5
sin A = 3/ akar 5
cos A = 4/ akar 5
cos 2 A = cos^2 A - sin ^2 A
= [tex][ \frac{4}{ \sqrt{5} } ]^2-[ \frac{3}{ \sqrt{5} } ]^2 = 16/5 - 9/5 = 7/5 [/tex]