You need to link with the math library:

gcc -o sphere sphere.c -lm

The error you are seeing: error: ld returned 1 exit status is from the linker ld (part of gcc that combines the object files) because it is unable to find where the function pow is defined.

Including math.h brings in the declaration of the various functions and not their definition. The def is present in the math library libm.a. You need to link your program with this library so that the calls to functions like pow() are resolved.

Like so if your program name is main.c and your compiler is gcc. You open the terminal and write gcc main.c -o main -lm

This happens because your Makefile doesn’t explain how to build tema1 (from Make’s perspective), so it uses its built-in rules:

• run depends on tema1;
• tema1 doesn’t have a definition, but there’s a C file, so Make tries to compile it using its default rule, which doesn’t specify -lm.

To fix this, say

tema1: tema1.c
        gcc tema1.c -o tema1 -lm

instead of build: tema1.c etc.

You can reduce repetition by using automatic variables:

tema1: tema1.c
        gcc $^ -o $@ -lm

To keep “named” rules (run, build etc.), make them depend on concrete artifacts (apart from clean, since it doesn’t produce anything), add separate rules for the concrete artifacts, and mark the “named” rules as phony (so Make won’t expect a corresponding on-disk artifact):

build: tema1

tema1: tema1.c
        gcc $^ -o $@ -lm

.PHONY: run build clean

It’s also worth changing clean so it doesn’t fail when there’s nothing to clean:

clean:
        rm -f *.o tema1