As I can "guess" from your question theta here stands for degree itself

Reason and Explanation to your answer:

Change in gravitational potential energy is = m*g*h

Where h is the distance above the initial line ,in your case its horizontal -

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Distance of man above horizontal --after he has climbed 1000m along the slope of 30degree inclination = 1000 sin(30)

Put the

value of g and m in the equation

your answer

= 100 * 1000 sin(30) * 9.8 Joule

= 10^5 * (1/2) * 9.8 J

=4.9 * 10^5 J

= 4.9e5 J

Tell me if you still need help