Answer:
The statement "if cos 0=0 then sec 0 is undefined" is true.
When the value of cos 0 is 0, it means the angle 0 is equal to 90 degrees or π/2 radians. At this angle, the value of the secant function, sec 0, is undefined as it is equal to 1/cos 0, and the denominator is equal to 0. Therefore, sec 0 cannot be equal to 0 when cos 0 is 0.
In general, it is not true that if a trigonometric function of an angle is equal to 0, then another trigonometric function of the same angle is also equal to 0. Each trigonometric function has its own unique properties and values that depend on the angle being used.