# Thread: Need help with 2 trigo questions

1. ## Need help with 2 trigo questions

Hi guys,

the first question is :

Find the time when I = 20sin(0.2(π)(t)+ π/3) is maximum : 0 ≤ t ≤ 12

and the second one is :

how to find I from the graph when t is given
I = 4sin100t + 3cos100t

for the second question what I did was, I made a table, assumed values from -5 to 5 and graphed, but I didn't know how to find I.

Any help would be greatly appreciated, I have a exam and am stuck with these 2 questions.

2. Originally Posted by jayjay
Hi guys,

the first question is :

Find the time when I = 20sin(0.2(π)(t)+ π/3) is maximum : 0 ≤ t ≤ 12
sine function has maximum value when angle equals $\frac{\pi}{2}$

$0.2{\pi}t+\frac{\pi}{3}=\frac{\pi}{2}$