In Exercises 1-4, use the trigonometric substitution to write the algebraic expression as a trigonometric function of , where 0 < < /

In Exercises 1-4, use the trigonometric substitution to write the algebraic expression as a trigonometric function of Θ, where 0 < Θ < π / 2.
1. √9 - x2, x = 3 cos Θ
2. √49 - x2, x = 7 sin Θ
3. √x2 - 4, x = 2 sec Θ
4. √9x2 + 25, 3x = 5 tan Θ