Update app.py

app.py

@@ -21,25 +21,25 @@ col1, col2, col3 = st.columns(3)
 
 with col1:
     if st.button('sin(x)', key='sin_button'):
-        expression += 'sin('
+        expression += 'sin()'
 with col2:
     if st.button('cos(x)', key='cos_button'):
-        expression += 'cos('
+        expression += 'cos()'
 with col3:
     if st.button('tan(x)', key='tan_button'):
-        expression += 'tan('
+        expression += 'tan()'
 
 col4, col5, col6 = st.columns(3)
 
 with col4:
     if st.button('log(x)', key='log_button'):
-        expression += 'log('
+        expression += 'log()'
 with col5:
     if st.button('sqrt(x)', key='sqrt_button'):
-        expression += 'sqrt('
+        expression += 'sqrt()'
 with col6:
     if st.button('exp(x)', key='exp_button'):
-        expression += 'exp('
+        expression += 'exp()'
 
 col7, col8 = st.columns(2)