IF Y=5+7C0S 4(0-7). FIND YWHEN 0=42 DEGREES. SMALLEST POSITIVE VALUE OF 0 FOR WHICH Y=1.5
y = 5 + 7cos 4(Ø-7)
when Ø = 42°
y = 5 + 7 cos 4(35)
= 5 + 7(-.76604444)
= -.3623
1.5 = 5+7cos 4(Ø-7)
cos 4(Ø-7) = (1.5-5)/7 = -.5
I know cos 60° = .5 and cos 120° = -.5
so 4(Ø-7) = 120
Ø-7 = 30
Ø = 37°